ALUMINIUM  AND  ITS  ALLOYS 


CALYPSO  WORKS. 


ALUMINIUM 

AND    ITS   ALLOYS 


THEIR  PROPERTIES,  THERMAL  TREATMENT 
AND   INDUSTRIAL   APPLICATION 


BY 

C.  GRARD 

LIEUTENANT-COLONEL 


TRANSLATED    BY 

C.  M.  PHILLIPS 

(NATURAL  SCIENCES  TRIPOS,  CAMBRIDGE) 
AND 

H.  W.  L.  PHILLIPS,  B.A.(CANTAB.),  A.I.C 

(LATE  SCHOLAR  OF  ST.  JOHN'S  COLLEGE,  CAMBRIDGE) 


NEW   YORK 

D.   VAN    NOSTRAND   COMPANY 

EIGHT  WARREN   STREET 

1922 


PRINTED   IN  GREAT   BRITAIN 


TRANSLATORS'    NOTE 

IN  this  translation  of  Col.  Grard's  book  on  "  Aluminium  and 
its  Alloys,"  the  original  text  has  been  adhered  to,  with  the 
exception  of  certain  of  the  appendices.  Certain  of  the  con- 
ditions of  the  French  aeronautical  specifications,  dealing  with 
sampling  and  identification  of  material,  have  not  been  con- 
sidered of  sufficient  interest  to  English  readers  to  warrant 
their  inclusion,  but  the  clauses  dealing  with  methods  and 
results  of  tests  have  been  given. 

The  centigrade  scale  of  temperatures  has  been  retained 
throughout  the  book. 

In  statistics  of  a  general  nature — as,  for  instance,  in  the 
case  of  approximate  output — the  tonne  and  ton  have  been 
regarded  as  equivalent.  In  exact  statistics,  however,  an 
accurate  conversion  has  been  made,  and  both  sets  of  values 
given. 

Where  prices  are  given,  the  rate  of  exchange  has  been  taken 
as  twenty-five  francs  to  the  pound  sterling,  whatever  the  date 
of  the  statistics  in  question. 

The  Tensile  Strength  and  Elastic  Limit  are  expressed  in 
kilogrammes  per  square  millimetre  and  in  tons  per  square 
inch — at  the  express  wish  of  the  author,  both  sets  of  values 
are  given  throughout  the  book,  in  the  tables  and  diagrams. 

In  the  case  of  Hardness  and  Cupping  Tests,  no  conversion 
has  been  attempted,  the  metrical  values  being  in  general  use 
in  this  country.  As  regards  Shock  Resistance  also,  no  con- 
version has  been  attempted.  On  the  Continent  the  term 
"  Resilience  "  is  employed  to  denote  the  energy  absorbed  in 
impact,  expressed  in  kilogramme-metres  per  square  centimetre 
of  cross  section  of  the  test  piece  at  the  bottom  of  the  notch, 
whilst  in  this  country,  it  is  employed  to  denote  a  different 
property.  The  area  of  cross  section  at  the  foot  of  the  notch 

vii 


viii  ALUMINIUM  AND  ITS  ALLOYS 

is  not  taken  into  consideration,  but  the  Shock  Resistance  is 
expressed  simply  by  the  energy,  in  foot-pounds,  absorbed  by 
impact  upon  a  test  piece  of  standard  dimensions. 

Assuming  that  the  conversion  from  kilogramme-metres 
per  square  centimetre  to  foot-pounds  is  an  arithmetical  possi- 
bility, the  figures  would  still  not  be  comparable,  as  the 
numerical  value  depends  to  a  very  great  extent  on  the  precise 
form  of  the  test  piece  employed,  especially  on  the  angle  and 
radius  at  the  foot  of  the  notch,  which  is  different  in  British 
and  Continental  practice. 

The  translators  would  wish  to  express  their  thanks  to 
Dr.  A.  G.  C.  Gwyer,  Chief  Metallurgist  to  the  British  Alu- 
minium Co.,  Ltd.,  for  his  valuable  advice  and  for  his  assistance 
in  the  reading  of  proofs. 

C.  M.  PHILLIPS. 

H.  W.  L.  PHILLIPS. 
WABBINGTON, 

November,  1920, 


AUTHOR'S    NOTE 

FOE  carrying  out  the  numerous  tests  required  for  this  work, 
we  have  utilised  the  following  Government  laboratories : — 

Le  Laboratoire  d'Essais  du  Conservatoire  national  des  Arts 
et  Metiers  (chemical  analyses,  mechanical  tests'). 

Le  Laboratoire  d'Essais  de  la  Monnaie  et  des  Medailles 
(chemical  analyses). 

Le  Laboratoire  de  la  Section  technique  de  I'Artillerie 
(chemical  analysis). 

Le  Laboratoire  de  1'Aeronautique  de  Chalais-Meudon 
(mechanical  tests  and  micrography). 

The  results,  from  which  important  deductions  have  been 
made,  possess,  therefore,  the  greatest  reliability. 

We  must  also  thank  the  following  private  laboratories : — 

Les  Laboratoires  de  la  Societe  Lorraine-Dietrich  (heat 
treatments  and  mechanical  tests), 

Les  Laboratoires  de  1'Usine  Citroen  (mechanical  tests  and 
micrography), 

for  the  readiness  with  which  they  have  placed  their  staff  and 
laboratory  material  at  the  disposal  of  the  Aeronautique.  By 
their  assistance  tests  were  multiplied,  inconsistencies  removed, 
and  the  delays,  incidental  to  the  carrying  out  of  this  work, 
minimised. 

Thanks  also  to  the  courtesy  of  the  Societe  de  Commentry- 
Fourchambault,  M.  Chevenard,  engineer  to  the  Company, 
has  investigated,  by  means  of  the  differential  dilatometer  of 
which  he  is  the  inventor,  the  critical  points  of  certain  alloys, 
whose  thermal  treatment  (quenching  and  reannealing)  is  of 
vital  importance. 


INTRODUCTION 

GENERAL   ARRANGEMENT   OF   CONTENTS 

THE  chief  characteristic  of  aluminium  is  its  low  density,  being 
second  only  to  magnesium,  and,  for  this  reason,  it  is  valuable 
for  aircraft.  Aluminium  would  be  ideal  if  this  lightness  could 
be  combined  with  the  mechanical  properties  of  the  Ferrous 
metals. 

The  ore,  from  which  alumina,  for  the  preparation  of  the 
metal,  is  extracted,  is  widely  distributed,  and  France  is 
particularly  favoured  in  this  respect. 

Whatever  the  method  of  working  and  thermal  treatment, 
pure  aluminium  only  possesses  a  low  strength,  which  prohibits 
its  use  for  articles  subjected  to  great  stresses.  Fortunately, 
certain  of  the  mechanical  properties  of  the  metal  can  be 
improved  by  the  addition  of  other  constituents,  and  in  some 
of  the  alloys  thus  formed  the  density  is  little  changed.  These 
are  the  so-called  light  alloys,  in  which  aluminium  is  a  main 
constituent,  and  which  can  be  divided  into  : — 

(i)  Light  alloys  of  low  strength, 
(ii)  Light  alloys  of  great  strength. 

In  others,  aluminium  is  present  in  such  small  quantity  that 
the  alloy  loses  its  characteristic  lightness,  to  the  advantage 
of  some  of  the  mechanical  properties.  The  most  important 
are  those  in  which  copper  is  the  principal  constituent.  These 
are 

(iii)  Heavy  alloys  of  great  strength. 

The  alloys  of  aluminium,  which  can  thus  be  divided  into 
three  groups,  are  very  numerous,  and  there  can  be  no  question 
of  considering  them  all.  In  each  group  we  shall  study  the 
ones  which  seem  the  most  interesting — those  in  which 
aluminium  plays  an  important  part.  We  shall  not  lay  much 

xi 


xii  ALUMINIUM  AND  ITS  ALLOYS 

stress  upon  those  in  which   aluminium  is  of  minor  import- 
ance. 

Adopting  the  classification  here  given,  arbitrary,  no  doubt, 
but  which,  from  the  aviator's  point  of  view,  has  its  value, 
since  it  puts  side  by  side  the  properties  of  lightness  and  strength, 
we  shall  consequently  arrange  this  work  according  to  the 
following  scheme : — 

Book  I. — Aluminium,  comprising  two  parts  : — 

Part  I.        Production  of  aluminium. 
Part  II.      Properties  of  aluminium. 

Book  II. — Alloys  of  aluminium,  comprising  three  parts  : — 

Part  III.     Light  alloys  for  casting  purposes. 
Part  IV.     Light  alloys  of  great  strength. 
Part  V.       Heavy  alloys  of  great  strength. 

Throughout,  a  large  number  of  tests  has  been  made  on 
each  type.  In  particular,  an  exhaustive  study  has  been 
carried  out  on  the  properties  as  functions  of  cold  work  and 
annealing,  and  on  the  hardness  at  all  temperatures.  The 
reliability  of  the  results  is  guaranteed  by  the  standard  of  the 
testing  laboratories,  and  by  the  reputation  of  the  experimenters. 


CONTENTS 


PAGE 

TRANSLATORS'  NOTE       ,        .,      •    ._       ...         .         .         .         .       vii 

AUTHOR'S  NOTE     .         .         .         *         .         .          .         «         .          .        ix 
INTRODUCTION  '*       3d 


BOOK  I 

ALUMINIUM 
PART  I— PRODUCTION  OF  ALUMINIUM 

CHAPTER 

I.     METALLURGY  OF  ALUMINIUM  .         .         .         ,         .     '    .         -'      3 
II.     WORLD'S  PRODUCTION    .         ,.        *         .         .......         9 

PART  II— PROPERTIES  OF  ALUMINIUM 

I.     PHYSICAL  PROPERTIES    .         *         .         .     '   .      T.        V        .       15 
II.     CHEMICAL  PROPERTIES — ANALYSIS  AND  GRADING     .  .       16 

III.     MECHANICAL  PROPERTIES        /        .         .         .        •,.•••.•         .       18 

A.  TENSILE  PROPERTIES — 

(i)  Variation  in  Tensile  Properties  with  amount  of  Cold  Work       20 
(ii)  Variation  in  Tensile  Properties  with  Annealing  Tempera- 
ture         *         -«        V        .          .          .          •          •          •       29 

B.  HARDNESS  AND  SHOCK  RESISTANCE — 

(i)  Variation  of  these  Properties  with  amount  of  Cold  Work  .       36 
(ii)  Variation  of  these  Properties  with  Annealing  Temperature       39 

C.  CUPPING   VALUES — DEPTH    OF   IMPRESSION   AND   BREAKING 

LOAD — 

(i)  Variation  of  these  Properties  with  amount  of  Cold  Work  .       41 
(ii)  Variation  of  these  Properties  with  Annealing  Temperature      44 

D.  SUMMARY          .         .         .         .         .  .  •  •  .  47 

E.  CONTEMPORARY  LITERATURE      .        >  ,*  .  •  .  51 
IV.    MICROGRAPHY  OF  ALUMINIUM         ...  .  .  .  •  .  56 

V.     PRESERVATION  OF  ALUMINIUM         .         .  *  ,  >  .  58 

VI.     SOLDERING  OF  ALUMINIUM      .  •      .        >  .  ,  .  .  62 

•tt 


xiv  ALUMINIUM  AND  ITS  ALLOYS 

BOOK  II 

ALLOYS  OF  ALUMINIUM 

PAGE 

CLASSIFICATION      .  67 

PABT  III— LIGHT    ALLOYS    OF    ALUMINIUM    FOR    CASTING 

PURPOSES 71 

PART  IV— LIGHT  ALLOYS  OF  GREAT  STRENGTH    ...       87 

CHAPTER 

I.  (a)  VARIATION   IN  MECHANICAL  PROPERTIES  WITH  AMOUNT  OF 

COLD  WORK 89 

(b)  VARIATION  IN  MECHANICAL   PROPERTIES  WITH  ANNEALING 

TEMPERATURE         .          .          .          .          .          .          .          .91 

II.  QUENCHING  ..........       96 

Effect  of  Quenching  Temperature  .....       96 

Rate  of  Cooling  .     " 101 

Ageing  after  Quenching         .          .          .          .          .          .          .103 

III.     VARIATION    IN    MECHANICAL   PROPERTIES   WITH   TEMPERATURE    ' 

OF  REANNEAL  AFTER  QUENCHING   .          .          .         .          .110 

IV.  RESULTS  OF  CUPPING  TESTS  AFTER  VARYING  THERMAL  TREAT- 

MENT .          .          .          .          .          .          .          .          .114 

V.  HARDNESS  TESTS  AT  HIGH  TEMPERATURES      .          .          .          .116 

PART  V— CUPRO-ALUMINIUMS  OR  ALUMINIUM  BRONZES       .     117 

I.     GENERAL  PROPERTIES    .         .         .         .         .         .         .         .118 

II.  MECHANICAL  PROPERTIES        ....... 

Alloy  Type  I  (90  %  Cu,  10  %  Al)  .          .          .          . 

Alloy  Type  II  (89  %  Cu,  10  %  Al,  1  %  Mn)  .... 
Alloy  Type  III  (81  %  Cu,  11  %  Al,  4  %  Ni,  4  %  Fe) 

IH.     MICROGRAPHY         ......... 

APPENDICES 

APPENDIX 

I.     ANALYTICAL  METHODS    ........ 

II.  EXTRACTS  FROM  THE  FRENCH  AERONAUTICAL  SPECIFICATIONS 
FOR  ALUMINIUM  AND  LIGHT  ALLOYS  OF  GREAT  STRENGTH 

III.  REPORT  OF  TESTS  CARRIED   OUT  AT  THE  CONSERVATOIRE  DES 

ARTS  ET  METIERS  ON  THE  COLD  WORKING  OF  ALUMINIUM 

IV.  REPORT  OF  THE  TESTS  CARRIED  OUT  AT  THE  CONSERVATOIRE  DES 
ARTS  ET  METIERS  ON  ANNEALING  THIN  SHEET  ALUMINIUM 
AFTER  COLD  WORK  ........ 

V.  REPORT  OF  TESTS  CARRIED  OUT  AT  THE  CONSERVATOIRE  DES 
ARTS  ET  METIERS  ON  THE  ANNEALING  OF  THICK  (10  MM.) 
SHEET  ALUMINIUM  AFTER  COLD  WORK  .... 

VI.  PAPER  SUBMITTED  TO  THE  ACADEMIE  DES  SCIENCES  BY  Lr.-CoL. 

GRARD,  ON  THE  THERMAL  TREATMENT  OF  LIGHT  ALLOYS  OF 
GREAT  STRENGTH 


LIST  OF  PLATES 

Calypso  Works  *         ."         .'         *         .'         .       ".          .      Frontispiece 

BOOK  I 

ALUMINIUM 

PART  I — PRODUCTION  AND  METALLURGY 

PLATE  TO  FACE  PAGE 

I     Norwegian  Nitrides  and  Aluminium  Company     .      .  ,.         »         .       13 
Photograph  1.  Works  at  Eydehavn  near  Arendal 

„          2.  Works  at  Tyssedal  on  the  Hardanger  Fjord 

II.     Saint  Jean  de  Maurienne       o  •,     .  .*        „         .          .          .          .       13 
Photograph  1.  Cylindrical  dam 

„  2.  Aqueduct  across  the  Arc 

III.     Engine-room  at  Calypso       ~".         .          .          .          .          .          .13 

PART  II — PROPERTIES  OF  ALUMINIUM 
I  AND  II.     Micrography  of  Aluminium      .          .          .          .          .          .57 

Photograph  1.  Aluminium  ingot,  chill  cast  (R.  J.  Anderson) 
„  2.  Aluminium  ingot,  sand  cast  (R.  J.  Anderson) 

„  3.  Aluminium,  cold  worked  (50  %) 

„  4.  Aluminium,  cold  worked  (100  %) 

„  5.  Aluminium,  cold  worked  (300  %) 

„  6.  Aluminium,  cold  worked  (300  %)  and  subsequently 

annealed  at  350°  for  10  minutes 
„  7.  Aluminium  annealed  at  595°  for  60  minutes  (R.  J. 

Anderson) 

„  8.  Aluminium  annealed  at  595°  for  4  hours  (R.  J. 

Anderson) 

BOOK  II 

ALLOYS  OF  ALUMINIUM 

PART  III — CASTING  ALLOYS 

III  AND  IIlA.     Micrography  of  casting  alloys     .....       86 
Photograph  1.  Copper  4  %,  aluminium  96  % 
„  2.  Copper  8  %,  aluminium  92  % 

„  3.  Copper  12  %,  aluminium  88  % 

„  4.  Copper  3  %,  zinc  12  %,  aluminium  85  % 

£  Copper  11  %,  tin  3  %,  nickel  1  %,  aluminium  85  % 
xv 


xvi  ALUMINIUM   AND  ITS  ALLOYS 

PLATE  TO   FACE    PAGE 

PART  V — CUPRO-ALUMINIUMS 

I.     Micrography  of  cupro-aluminium,  Type  I,  forged  and  annealed     143 
Photograph  1.  As  forged.          X  60 

2.  As  forged.          X225 
„         3.  Forged  and  subsequntly  annealed  at  300°. 

X60 

„         4.  Forged  and  subsequently  annealed  at  300°. 
X225 

IB.     Micrography  of  cupro-aluminium,  Type  I,  showing   eutectic 

structure      .........      143 

Photograph  A.  Etched  with  alcoholic  FeCl3.  X  500 

( Porte  vin) 
„         B.  Etched     with     alcoholic     FeCl3.  X  870 

(Portevin) 

,,       C.  Etched  with  alcoholic  FeCl3,  showing  cellular 
and    lamellar    formations.          X  500    (Por- 
tevin) 

„       D.  Etched  with  alcoholic  FeCl3,  showing  eutectic 
4--y.      Hypereutectoid    alloy.  X  200 

(Portevin) 

II.     Micrography  of  cupro-aluminium,  Type  I,  forged  and  subse- 
quently annealed.          .  .          .          .          .          .143 

Photograph  5.  Forged  and  subsequently  annealed  at  700°. 

X60 
„  6.  Forged  and  subsequently  annealed  at  700°. 

X225 
„  7.  Forged  and  subsequently  annealed  at  900°. 

X60 

„  8.  Forged  and  subsequently  annealed  at  900°. 

X225 

III.  Micrography  of  cupro-aluminium,  Type  I,  forged  and  subse- 

quently quenched  .          .          .          .          .          .          .143 

Photograph  9.  Forged    and    subsequently    quenched    from 

500°.          x  60 
„          10.  Forged    and    subsequently    quenched    from 

500°.          X  225 
„          11.  Forged    and    subsequently    quenched    from 

600°.          X  60 

„          12.  Forged    and    subsequently    quenched    from 
600°.          X  225 

IV.  Micrography  of  cupro-aluminium,  Type  I,  forged  and  subse- 

quently quenched  (Breuil)      .          .          .          .          .          .143 

Photograph  13.  Forged  and    subsequently    quenched    from 

700°.          X  60 

„          14.  Forged  and    subsequently    quenched    from 

700°.          X  225 

„          15.  Forged  and    subsequently    quenched    from 

800°.          X  60 

„          16.  Forged  and    subsequently    quenched    from 
800°.          X  225 


LIST  OF  PLATES  xvii 

PLATE  TO    FACE   FAQE 

V.     Micrography  of  cupro-aluminium,  Type  I,  forged  and  subse- 
quently quenched  (Breuil)      .          .          .          .          .          .143 

Photograph  17.  Forged   and   subsequently   quenched   from 

900°.          X  60 

„          18.  Forged  and  subsequently    quenched    from 
900°.          X  225 

VI.     Micrography  of  cupro-aluminium,  Type  I,  forged,  quenched, 

and  reannealed .144 

Photograph  19.  Forged,  quenched  from  900°,  reannealed  at 

300°.          X  60 
„  20.  Forged,  quenched  from  900°,  reannealed  at 

300°.          X  225 
„  21.  Forged,  quenched  from  900°,  reannealed  at 

600°.          X  60 

„  22.  Forged,  quenched  from  900°,  reannealed  at 

600°.          x  225 

VII.     Micrography  of  cupro -aluminium,  Type  I,  forged,  quenched, 

and  reannealed     .         "4 '•••"      .          *;       .*        '*    ,      «          .      144 
Photograph  23.  Forged,  quenched  from  900°,  reannealed  at 

700°.          X  60 
„  24.  Forged,  quenched  from  900°,  reannealed  at 

700°.          X225 
„  25.  Forged,  quenched  from  900°,  reannealed  at 

800°.          X  60 

„  26.  Forged,  quenched  from  900°,  reannealed  at 

800°.          x  225 

VIII.     Micrography  of  cupro-aluminium,  Type  I,  cast  and  annealed  .     144 
Photograph  27.  As  cast.          x  60 

28.  As  cast.          x225 

„  29.  Cast  and  annealed  at  800°.          X  60 

„  30.  Cast  and  annealed  at  800°.          X  225 

IX.     Micrography  of  cupro-aluminium,  Type  I,  cast  and  annealed  .     144 
Photograph  31.  Cast  and  annealed  at  900°.          X  60 

„  32.  Cast  and  annealed  at  900°.          X  225 

X.     Micrography  of  cupro-aluminium,  Type  I,  cast  and  quenched     144 

Photograph  33.  Cast  and  quenched  from  500°.          X  60 

„  34.  Cast  and  quenched  from  600°.          X  60 

35.  Cast  and  quenched  from  700°.          x  60 

„  36.  Cast  and  quenched  from  800°.          x  60 

„  37.  Cast  and  quenched  from  900°.          x  60 

XI.     Micrography  of  cupro-aluminium,   Type   II,  forged  and  an- 
nealed         .          .          .          *          .          .          .          .          .144 
Photograph  38.  As  forged.          x  60 
„  39.  As  forged.          x  225 

„  40.  Forged  and  subsequently  annealed  at  8CO°. 

X60 
„  41.  Forged  and  subsequently  annealed  at  800°. 

x225 
6 


xviii  ALUMINIUM    AND  ITS  ALLOYS 

PLATE  TO    FACE    PAGE 

XII.     Micrography  of  cupro-aluminium,  Type  II,  quenched  and  re- 
annealed      .........      144 

Photograph  42.  Quenched  from   900°,  reannealed  at   600°. 

X60 

„  43.  Quenched  from   900°,  reannealed  at   600°. 

X225 

XIII.  Micrography  of  cupro-aluminium,  Type  III,  forged  and  an- 

nealed  144 

Photograph  44.  As  forged.          x  60 
„  45.  As  forged.          x  225 

„  46.  Forged  and  annealed  at  600°.         x  60 

„  47.  Forged  and  annealed  at  600°.          x  225 

XIV.  Micrography  of  cupro-aluminium,  Type  III,  forged  and  an- 

nealed   144 

Photograph  48.  Forged  and  annealed  at  800°.          x  60 
„  49.  Forged  and  annealed  at  900°.          x  225 

XV.     Micrography    of     cupro-aluminium,    Type     III,    forged    and 

quenched     .........     144 

Photograph  50.  Quenched  from  500°.          x  60 
„  51.  Quenched  from  500°.          x  225 

„  52.  Quenched  from  800°.          x  60 

„  53.  Quenched  from  800°.          X  225 

XVI.     Micrography    of     cupro-aluminium,    Type     III,    forged    and 

quenched   .........   144 

Photograph  54.  Quenched  from  900°.          x  60 
„  55.  Quenched  from  900°.          X  225 

XVII.     Micrography  of  cupro-aluminium,  Type   III,   quenched  and 

reannealed  .          .          .          .          .          .          .          .          .      144 

Photograph  56.  Quenched  from  900°,  reannealed  at   500°. 

X60 
„  57.  Quenched  from   900°,  reannealed   at  500°. 

X225 
„  58.  Quenched  from  900°,   reannealed  at   600°. 

X60 

„  59.  Quenched  from   900°,   reannealed  at  600°. 

X225 


LIST  OF  ILLUSTRATIONS  IN  TEXT 

BOOK  I 

ALUMINIUM 
PART  I — PRODUCTION  AND  METALLURGY 

FIGURE  PAGE 

1.  Melting-point  curve  of  mixtures  of  cryolite  and  alumina       .          .          5 

2.  World's  production  of  bauxite  .,' .       •  ?.-•••  f^-*  \  ..-.•       \  .         9 

3.  Map  of  the  South  of  France,  showing  distribution  of  bauxite  and 

situation  of  aluminium  and  alumina  factories  ,          .          .        11 

PART  II — PROPERTIES 

4.  Variation  in  mechanical   properties  (tensile)  of    thin  aluminium 

sheet  (1  mm.  thick)  with  cold  work         ..        *  ^      \.          .          .23 

5.  Variation  in  mechanical  properties  (tensile)  of  thick  aluminium 

sheet   (10  mm.   thick)  cut  longitudinally  to  the  direction  of 
rolling,  with  cold  work .         ..  •-    .,.*,•     ~- v  ,.  *V^v;%^       %*,        .       26 

6.  Variation  in  mechanical  properties  (tensile)  of  thick  aluminium 

sheet  (10  mm.  thick)  cut  transversely  to  the  direction  of  rolling, 
with  cold  work     .          .          ,  •  .          .  .          .27 

7.  Variation  in  mechanical  properties  (tensile)  of  aluminium  with 

annealing  temperature.    Test  pieces  0-5  mm.  thick.    Prior  cold 
work  50  %.         Y         .          .      .-'".,"      .         Y       Sv      .          .       28 

8.  Variation  in  mechanical  properties  (tensile)  of  aluminium  with 

annealing  temperature.    Test  pieces  0-5  mm.  thick.    Prior  cold 
work  100  %          .          .          .        J. 29 

9.  Variation  in  mechanical  properties  (tensile)  of  aluminium  with 

annealing  temperature.    Test  pieces  0-5  mm.  thick.     Prior  cold 
work  300  %        '.          .  '  .*•' 30 

10.  Variation  in  mechanical  properties  (tensile)  of  aluminium  with 

annealing  temperature.    Test  pieces  2-0  mm.  thick.     Prior  cold 
work  50  %  .          .          .          .          .          .          .          .          .          .31 

11.  Variation  in  mechanical  properties  (tensile)  of  aluminium  with 

annealing  temperature.     Test  pieces  2-0  mm.  thick.     Prior  cold 

work  100  % 32 

xix 


xx  ALUMINIUM  AND  ITS  ALLOYS 

FIGUBE  PAGE 

12.  Variation  in  mechanical  properties  (tensile)  of  aluminium  with 

annealing  temperature.    Test  pieces  2-0  mm.  thick.    Prior  cold 
work  300  % 3 

13.  Variation  in  mechanical  properties  (tensile)  of  aluminium  with 

annealing  temperature.    Test  pieces  10  mm.  thick.     Prior  cold 
work  100  % 35 

14.  Variation  in  mechanical  properties  (tensile)  of    aluminium  with 

annealing  temperature.    Test  pieces  10  mm.  thick.    Prior  cold 
work  300% 36 

15.  Variation  in  mechanical  properties  (hardness  and  shock)  with  cold 

work.    Test  pieces  10  mm.  thick    .          .          .          .          .          .37 

16.  Variation  in  mechanical  properties  (hardness  and  shock)  on  anneal- 

ing after  100  %  cold  work.    Test  pieces  10  mm.  thick        .  3£ 

1 7.  Variation  in  mechanical  properties  (hardness  and  shock)  on  anneal- 

ing after  300  %  cold  work.    Test  pieces  10  mm.  thick        .          .       40 

18.  Pereoz  apparatus  for  cupping  tests  ......       42 

19.  Cupping  tests.   Variation  in  breaking  load  and  depth  of  impression 

with  cold  work.    Test  pieces  2-0,  1-5,  1-0,  0-5  mm.  thick  .          .       43 

20.  Cupping  tests.    Variation  in  breaking  load  and  depth  of  impression 

with  thickness  at  specified  amounts  of  cold  work  (0,  50,  100, 
and  300  %) 44 

21.  Cupping  tests.    Variation  in  breaking  load  and  depth  of  impression 

on  annealing  after  50  %  cold  work.    Test  pieces  0-5  mm.  thick       45 

22.  Cupping  tests.    Variation  in  breaking  load  and  depth  of  impression 

on  annealing  after  100  %  cold  work.    Test  pieces  0-5  mm.  thick       46 

23.  Cupping  tests.    Variation  in  breaking  load  and  depth  of  impression 

on  annealing  after  300  %  cold  work.    Test  pieces  0-5  mm.  thick       47 

24.  Cupping  tests.    Variation  in  breaking  load  and  depth  of  impression 

on  annealing  after  50  %  cold  work.    Test  pieces  20  mm.  thick       48 

25.  Cupping  tests.    Variation  in  breaking  load  and  depth  of  impression 

on  annealing  after  100  %  cold  work.    Test  pieces  2-0  mm.  thick       49 

26.  Cupping  tests.    Variation  in  breaking  load  and  depth  of  impression 

on  annealing  after  300  %  cold  work.    Test  pieces  2-0  mm.  thick       50 

27.  Cupping  tests.     Variation  in  depth  of  impression  with  thickness. 

Annealed  aluminium  sheet  (R.  J.  Anderson)  ....        53 

28.  Cupping  tests.     Variation  in  depth  of  impression  with  thickness. 

Cold  worked  aluminium  sheet  (R.  J.  Anderson)        ...       54 

29.  Aluminium  sheet.     Effect  of  annealing  for  different  lengths  of 

time  at  430°  (R.  J.  Anderson) 55 


LIST  OF  ILLUSTRATIONS  IN   TEXT  xxi 

BOOK  II 

ALLOYS  OF  ALUMINIUM 

FIGURE  PAGE 

30.  Equilibrium  diagram  of  copper-aluminium  alloys  (Curry)    .          .       69 

PART  III — CASTING  ALLOYS 
306.  Hardness  of  aluminium  at  high  temperatures  (500  kg.  load)  .       73 

31.  Hardness  of  aluminium -copper  alloy  (4  %  Cu)  at  high  tempera- 

tures (500  and  1000  kg.)  .  .  ..;.       :  >  .         77 

32.  Hardness  of  aluminium-copper  alloy  (8  %  Cu)  at  high  tempera- 

tures (500  and  1000  kg.)         .          .          .          .          .          *   ,      .       77 

33.  Hardness  of  aluminium -copper  alloy  (12  %  Cu)  at  high  tempera- 

tures (500  and  1000  kg.)         .       .-,.          .         1.          .          ..         .       79 

34.  Variation  in  hardness  with  copper  content  (load  500  kg. )     Tem- 

peratures 0°,  100°,  200°,  300°,  350°,  400°         .„        . ,    •  .  *  «     .       79 

35.  Hardness  of  aluminium -zinc -copper  alloy  (12  %  Zn,  3  %  Cu)  at 

high  temperatures  (500  and  1000  kg.  load)      .       •,.          .          .       81 

36.  Hardness  of  aluminium-copper-tin-nickel  alloy  (11%  Cu,  3  %  Sn, 

1  %  Ni)  at  high  temperatures  (500  and  1000  kg.  load)      .          .       83 

37.  Melting-point  curve  for  zinc -aluminium  alloys    .          ...       83 

PART  IV — LIGHT  ALLOYS  OF  GREAT  STRENGTH 

38.  Tensile  test  piece  (thick  sheet)  .         v        ..    '     .' •       'i.    .      „':       .       89 

39.  Tensile  test  piece  (thin  sheet)    .     t>  4          .';     ,  ,/       .  '       ,,        .       89 

40.  Variation  in  mechanical  properties  (tensile  and  shock)  of  duralumin 

with  cold  work.    Metal  previously  annealed  at  450°  and  cooled 

in  air.    Test  pieces  cut  longitudinally  to  direction  of  rolling      .       90 

41 .  Variation  in  mechanical  properties  (tensile  and  shock)  of  duralumin 

with  cold  work.    Metal  previously  annealed  at  450°  and  cooled 

in  air.    Test  pieces  cut  transversely  to  direction  of  rolling  .          .        91 

42.  Variation  in  mechanical  properties  (tensile,  hardness,  and  shock)  of 

duralumin,  with  annealing  temperature.  Metal  subjected  to 
50  %  cold  work,  annealed,  and  cooled  very  slowly.  Longitudinal 
test  pieces  .  .  .  .  .  .  .92 

43.  Variation    in    mechanical    properties    (tensile    and    shock)     of 

duralumin,  with  annealing  temperature.  Metal  subjected  to 
50  %  cold  work,  annealed,  and  cooled  in  air.  Longitudinal  test 
pieces  .  '.  •*'.-  V  *.  '  j  •'  .  .  .  .  93 

44.  Variation  in  mechanical  properties  (tensile,  hardness,  and  shock) 

of  duralumin,  with  annealing  temperature.     Metal  subjected  to 

50  %  cold  work,  annealed,  and  cooled  very  slowly.    Transverse 

test  pieces    .          .          .          .         .'          .          I*'      .  .93 

45.  Variation    in     mechanical     properties     (tensile    and     shock)    of 

duralumin,  with  annealing  temperature.  Metal  subjected  to 
50  %  cold  work,  annealed,  and  cooled  in  air.  Transverse  test 
pieces  .  .  ,  .  .  .  .  .  .  .  94 


xxii  ALUMINIUM  AND  ITS   ALLOYS 

FIGURE  PAGE 

46.  Duralumin  compared  with  pure  aluminium,  using  dilatometer     .        96 

47.  Variation  in  mechanical  properties  of  duralumin  with  time  after 

quenching  (from  300°) 97 

48.  Variation  in  mechanical  properties  of  duralumin  with  time  after 

quenching  (from  350°) 98 

49.  Variation  in  mechanical  properties  of  duralumin  with  time  after 

quenching  (from  400°)  ........        99 

50.  Variation  in  mechanical  properties  of  duralumin  with  time  after 

quenching  (from  450°)  ........       99 

51.  Variation  in  mechanical  properties  of  duralumin  with  time  after 

quenching  (from  500°) 100 

52.  Variation  in  mechanical  properties  of  duralumin  with  time  after 

quenching  (from  550°) 100 

53.  Variation  in  mechanical  properties  of  duralumin  with  quenching 

temperature  (after  8  days)     .          .          .          .          .          .          .101 

54.  Variation  in  mechanical  properties  of  duralumin  with  time  after 

quenching  from  475°  (during  first  48  hours)     .          .          .          .103 

55.  Variation  in  mechanical  properties  of  duralumin  with  time  after 

quenching  from  475°  (during  first  8  days)         .          .          .          .104 

56.  Variation  in  mechanical  properties  of  duralumin  with  annealing 

temperature.   Metal  quenched  from  475°,  reannealed,  and  cooled 
very  slowly.          .          .          .          .          .          .          .          .          .110 

57.  Variation  in  mechanical  properties  of  duralumin  with  annealing 

temperature.   Metal  quenched  from  475°,  reannealed,  and  cooled 

in  air  .          .          .          .          .          .          .          .          .          .111 

58.  Variation  in  mechanical  properties  of  duralumin  with  annealing 

temperature.      Metal   quenched    from    475°,    reannealed,    and 
quenched  in  water         .          .          .          .          .          .          .          .112 

59.  Duralumin.    Cupping  tests.    Variation  in  breaking  load  and  depth 

of  impression  with  annealing  temperature.    Anneal  followed  by 
cooling  at  various  rates          .          .          .          .          .          .          .114 

60.  High  temperature  hardness  tests  (500  kg.)  on  duralumin  quenched 

from  475° 116 

PART  V — CUPRO-ALUMINITJMS 

61.  Tensile  test  piece  (round  bars)  ....... 

62.  Aluminium  bronze,  Type  I,  critical  points          .... 

63.  Aluminium  bronze,  Type  I,  allowed  to  cool  in  furnace 

64.  Aluminium  bronze,  Type  I,  slow  cooling     ..... 

65.  Aluminium  bronze,  Type  I,  temperature  not  exceeding  Ac3 

66.  Variation  in  mechanical  properties  (tensile  and  impact)  with  an- 

nealing temperature.    Cast  aluminium  bronze,  Type  I  (Cu  90  %, 
Al  10  %) .          . 


LIST  OF  ILLUSTRATIONS   IN  TEXT         xxiii 

FIGURE  PAGE 

67.  Variation  in  mechanical  properties  (tensile  and  impact)  with  an- 

nealing temperature.    Forged  aluminium  bronze,  Type  I  .124 

68.  Variation   in   mechanical   properties    (tensile   and   impact)   with 

quenching  temperature.    Cast  aluminium  bronze,  Type  I  .     125 

69.  Variation   in   mechanical   properties    (tensile   and   impact)   with 

quenching  temperature.    Forged  aluminium  bronze,  Type  I      .      126 

70.  Variation   in   mechanical   properties    (tensile   and   impact)    with 

temperature  of  reanneal  after  quenching  from  700°.     Forged 
aluminium  bronze,  Type  I     .          .          *          ,          .          ,          ,     127 

71.  Variation    in    mechanical    properties    (tensile    and  impact)  with 

temperature  of  reanneal  after  quenching  from  800°.     Forged 
aluminium  bronze,  Type  I     .          .          .  „        .          .          ?          .      128 

72.  Variation   in   mechanical   properties    (tensile   and   impact)   with 

temperature  of  reanneal  after  quenching  from  900°.     Forged 
aluminium  bronze,  Type  I.          *   .       •          »         .,          ,          ,129 
726.  High -temperature  hardness  tests  (500  kg.)  on  aluminium  bronze, 

Type  I,  as  cast,  worked,  and  heat  treated        ...         .          .          »     131 

73.  Aluminium  bronze,  Type  II,  critical  points          »         *         ...     132 

74.  Aluminium  bronze,  Type  II       .          .          .          ...      .          .     132 

75.  Variation    in    mechanical   properties    (tensile   and   impact)   with 

annealing   temperature.     Forged  aluminium  bronze,  Type  II 

(Cu  89  %,  Mn  1  %,  Al  10  %)  .     133 

76.  Variation   in   mechanical   properties    (tensile   and   impact)    with 

quenching  temperature.    Forged  aluminium  bronze,  Type  II      .      134 

77.  Variation   in   mechanical   properties    (tensile   and   impact)   with 

temperature  of  reanneal  after  quenching  from  800°.     Forged 
aluminium  bronze,  Type  II   .          *          .          .          .          .          .135 

78.  Variation   in   mechanical   properties    (tensile   and   impact)   with 

temperature  of  reanneal  after  quenching  from  900°.     Forged 
aluminium  bronze,  Type  II   ..          .          .          .          .          .135 

786.  High -temperature  hardness  tests  (500  kg.)  on  aluminium  bronze, 

Type  II.     Quenched  from  900°,  reannealed  at  600°.          ,          .136 

79.  Aluminium  bronze,  Type  III,  critical  points  (dilatometer)   .          .      137 

80.  Aluminium   bronze,  Type  III,  critical  points,  temperature  time 

curve  .          .          .          .          .          .          .  ^  .          .      138 

81.  Variation   in   mechanical   properties    (tensile   and   impact)   with 

annealing  temperature.     Forged  aluminium  bronze,  Type  III 

(Cu  81  %,  Ni  4  %,  Fe  4  %,  Al  11  %)     .         ...          .          .     138 

82.  Variation   in   mechanical   properties    (tensile   and   impact)    with 

quenching  temperature.     Forged  aluminium  bronze,  Type  III     139 

83.  Variation   in   mechanical   properties    (tensile   and   impact)   with 

temperature  of  reanneal  after  quenching  from  900°.     Forged 
aluminium  bronze,  Type  III  .          .'          i'         .'        .    '       .      140 

836.  High -temperature  hardness  tests  (500  kg.)  on  aluminium  bronze, 

Type  III.    Annealed  at  900°  .  ....      141 


BOOK  I 
ALUMINIUM 


Aluminium  and  its  Alloys 

PART  I 
PRODUCTION  OF  ALUMINIUM 

CHAPTER  I 
METALLURGY   OF   ALUMINIUM 

ALUMINIUM  is  prepared  by  the  electrolysis  of  alumina  dissolved 
in  fused  cryolite.  The  electric  energy  is  derived  from  water- 
power.  The  essential  materials  for  the  process  are  therefore 

(i)  Alumina, 
(ii)  Cryolite. 
ALUMINA. 

Alumina  is  prepared  from  bauxite  [(Al,  Fe)2082H20]  or 
from  certain  clays  [Al2O3.2Si02]. 

(a)  From  Bauxite. 

Bauxite  is  a  clay-like  substance,  whitish  when  silica  is  pre- 
dominant, or  reddish  when  oxide  of  iron  is  largely  present.  It 
is  found  in  great  quantity  in  France,  in  the  neighbourhood  of 
the  village  of  Baux,  near  Aries  (hence  the  name,  bauxite), 
and  more  commonly  in  the  Departments  of  Bouches-du- 
Rhone,  Gard,  Ariege,  Herault,  and  Var.  It  is  found  in  Calabria, 
Iceland,  Styria,  Carniola,  and  in  the  United  States  of  America 
in  Georgia,  Arkansas,  Alabama,  and  Tennessee. 

Commercial  bauxite  has  the  following  composition  : — * 

Alumina  (A12O8)  .  57  %  A  premium  of  -20  to  40  francs 

per  kilo  (roughly  Id.  to  2d.  per 
Ib.)  was,  in  1909,  paid  for  each 
per  cent  over  60  %. 

Silica  (SiO,)  .  3  %  If  below  2  %,  a  premium  of  -20 

fr.  per  kg.  (roughly  Id.  per  Ib.) 
was  paid  per  -1  %. 

*  Lodin,  "  Annales  des  Mines,"  Nov.,  1909. 


ALUMINIUM  AND  ITS  ALLOYS 

Iron  Oxide  (Fe203)  .     14  %     For  each  per  cent  above  this 

value,  up  to  the  maximum 
allowed,  17  %,  -20  fr.  per  kg. 
(roughly  Id.  per  Ib.)  was  de- 
ducted. Some  works  allow  as 
much  as  25  %  Fe203. 

White  bauxites  are  chiefly  used  for  the  production  of 
aluminium  sulphate  and  the  alums.  Red  bauxites  form  the 
raw  material  for  the  preparation  of  alumina,  and  therefore  of 
aluminium.  Intermediate  or  refractory  bauxites,  fused  in  an 
electric  furnace,  give  artificial  corundum. 

Bauxite  is  treated  either  by  Deville's  method  or  by  that  of 
Bayer,  the  latter  being  almost  exclusively  employed.  A  third 
method  depends  upon  the  production  of  aluminium  nitride. 
This  is  obtained  by  heating  bauxite  in  air  to  1800°-1 900°  in 
an  electric  furnace.  It  is  then  decomposed  in  an  autoclave  in 
presence  of  soda  solution,  giving  (i)  ammonia,  used  as  a  manure 
in  the  form  of  its  sulphate,  (ii)  sodium  aluminate,  from  which 
commercially  pure  alumina  can  be  obtained. 

(b)  From  Clay. 

Clays  are  treated  either  by  the  Cowles-Kayser  or  by  the 
Moldentrauer  process,  yielding  alumina  from  which  aluminium 
is  prepared  by  electrolysis. 

CRYOLITE. 

Cryolite,  which  is  so  called  on  account  of  its  high  fusibility, 
is  a  double  fluoride  of  aluminium  and  sodium  of  the  formula 
Al2F6.6NaF.  It  is  obtained  from  Western  Greenland,  where 
it  occurs  in  beds  up  to  one  metre  thick,  but  the  high  price  of 
this  material  has  led  to  the  manufacture  of  synthetic  cryolite, 
using  calcium  fluoride  (fluor-spar),  which  is  found  in  con- 
siderable quantities. 

ELECTRIC  FURNACES. 

The  furnace  consists  of  a  vat,  containing  electrodes  (anodes), 
and  a  conducting  hearth  (the  cathode)  sloping  towards  the 
tapping  hole.  Aluminium,  formed  by  electrolysis  of  the 
alumina,  collects  on  the  floor  of  the  vat ;  oxygen  is  liberated 
at  the  anode,  which  it  attacks,  forming  carbon  monoxide 
and  finally  carbon  dioxide. 

The  current  is  used  at  a  potential  difference  of  8  to  10 
volts,  and  at  a  density  of  1  -5  to  3  amps,  per  square  centimetre 
of  electrode.  The  furnace  is  regulated  by  raising  or  lowering 
the  electrodes,  or  by  varying  the  quantity  of  alumina.  When 


METALLURGY  OF  ALUMINIUM 


the  latter  is  present  in  small  quantities,  the  fluorides  decom- 
pose, and  the  voltage  (normally  8-10  volts)  rises.  This  is 
indicated  by  the  change  in  intensity  of  a  lamp.  In  this  case 
sodium  is  formed  at  the  cathode,  and  has  deleterious  effects 
on  the  quality  of  the  metal. 

METHOD  OF  TAPPING  ALUMINIUM. 

Since  aluminium  is  very  easily  oxidised,  it  cannot  be  sub- 
jected to  a  final  refining  process,  but  must  possess,  at  this  early 
stage,  its  commercial  purity.  It  is  therefore  essential  to  avoid 
oxidation  during  the  manufacturing  process,  and  the  cryolite, 


ioooc 


975 


950 


925^ 


9001 


O  5  10  15  20 

FIG.  1. — Melting-point  Curve  of  Mixtures  of  Al2F6.6NaF  and  A12O3.     (Pryn.) 

containing  alumina  in  solution,  furnishes  the  means  to  that 
end.  The  metallic  aluminium  must  not  float,  but  sink  to  the 
bottom  of  the  vat,  where  the  fused  salts  protect  it  against 
oxidation.  The  salts  must  have,  therefore,  a  lower  density 
than  the  metal. 

The  theory  of  the  preparation  of  the  metal  is  made  clear 
by  a  study  of  the  melting-point  curve  of  mixtures  of  cryolite 
(Al2F6.6NaF)  and  alumina,  due  to  Pryn.* 

Pure  cryolite  melts  at  1000°,  and  the  mixture  of  maximum 
fusibility  (915°)  consists  of  95  %  cryolite  with  5  %  alumina. 

As  the  alumina  content  increases  from  5  to  20  %,  the  melting 
point  rises  from  915°-1015°,  the  curve  of  fusibility  consisting 
of  portions  of  straight  lines  of  varying  slope. 

*  Pryn,  "  Mineral  Industry,"  Vol.  XV,  p.  19. 


6  ALUMINIUM  AND  ITS  ALLOYS 

Certain  definite  mixtures  of  cryolite,  calcium  fluoride  or 
aluminium  fluoride,  and  alumina  have  still  lower  melting 
points,  the  limiting  value  being  800°  (Hall).  In  practice  the 
melting  point  of  the  bath  ranges  from  900°-950°  ;  it  is  there- 
fore evident  that  the  manufacturer  has  a  choice  of  mixtures 
which  will  fulfil  these  conditions. 

The  respective  densities  of  the  cryolite  mixture  and  of 
aluminium  are : — 

Cryolite  mixture      .      fsolid>      2'92 
lliquid,    2-08 

Aluminium   ,  /solid,     2-6 

lliquid,    2-54 

which  satisfy  the  conditions  above  mentioned. 

The  furnace  is  tapped  about  every  forty-eight  hours.  The 
liquid  flows  first  into  a  receiver,  in  which  the  fluorides  carried 
over  are  retained  in  the  solid  state,  and  from  this  vessel  into 
moulds,  giving  ingots  which  can  easily  be  divided. 

OUTPUT. 

According  to  Flusin,  the  output  is  as  follows  : — 

210  kg.  to  275  kg.  of  aluminium  per  kilowatt-year 
(i.e.  4631b.-606-l  Ib.  per  kw.  year), 

or,       154-200  kg.  per  "  Force  de  cheval  "  year 
(i.e.  344-1-447  Ib.  per  horse-power  year), 

which  works  out  at : — 

31-41  kilowatt  hours  per  kg.  of  aluminium 
(i.e.  14-1-18-7  kw.  hours  per  Ib.), 

assuming  an  average  efficiency  of  70  %,  and  a  maximum 
efficiency  of  78  %. 

CONSUMPTION  OF  MATERIAL. 

Alumina  per  kg.  of  aluminium  :    theoretically  1-888  kg. 

practically      2-0  kg. ; 

formerly  this  figure  was  higher,  but  then  the  voltage  was  15 
to  20  v.  (i.e.  1-888  tons  and  2-0  tons  of  alumina  per  ton  of 
aluminium,  respectively). 

Cryolite,  per  kg.  of  aluminium  0-150  kg.  on  an  average 
(i.e.  3  cwt.  cryolite  per  ton  of  aluminium). 

Calcium  and  aluminium  fluorides,  per  kg.  of  aluminium, 
0-200  kg.  (i.e.  4  cwt.  per  ton  of  aluminium). 

Anodes,  per  kg.  of  aluminium,  0-8  to  1-0  kg.  (i.e.  16  cwt,-l 
ton  per  ton  of  aluminium), 


METALLURGY  OF  ALUMINIUM 


From  these  data  we  can  draw  the  following  conclusions  con- 
cerning the  cost  price.  For  the  production  of  a  ton  of  alu- 
minium two  tons  of  alumina  are  required  and  also  one  ton  of 
carbon  for  the  electrodes  ;  while,  for  the  production  of  the 
alumina  itself,  six  tons  of  carbon  are  required.  Since  alumina 
is  made  near  the  spot  where  bauxite  is  found,  it  is  necessary 
to  consider  the  effect  of  the  following  transport  charges  upon 
the  cost  price  : — 

(i)  Carriage  qf  carbon  to  alumina  works, 
(ii)  Carriage  of  carbon  to  aluminium  works, 
(iii)  Carriage  of  alumina  to  aluminium  works. 

It  is  evident  that  those  aluminium  works  which  can  obtain 
only  hydraulic  power  locally,  so  that  the  transport  charges, 
just  mentioned,  are  heavy,  are  at  a  disadvantage  in  competing 
with  works  more  favourably  situated.  The  French  aluminium 
works  are  especially  favoured  in  this  respect.* 

ROLLING  OF  ALJJMINIUM. 

The  ingots  of  aluminium  are  first  melted  in  a  furnace — often 
a  revolving  furnace,  heated  by  gaseous  fuel.  The  aluminium 
is  then  cast  into  slabs,  which,  in  France,  usually  are  of  the 
following  dimensions  : — 

(1)  S0kg.=0-55m.  xO-65m.  xO-08m.(21-6in.  x25-5in.  x3-15in.) 

(2)  55  kg.=0-56m.  x  0-66m.  x  0-055m.(22-0in.  X  25-9in.  X  2-16in.) 

(3)  27  kg.=0-35m.  x  0-7m.  X  0-04m.(13-8in.  X 27-5in.  X  l-57in.) 

*  Lodin  established  in  the  following  manner  the  cost  price  in  1909  : — 


Alumina  .     1  -950  kg.  per  kg.  of  Al  at  0-3  fr.  per  kg. 

Cryolite  .          .     0-125  kg.      „  „  0-6 

Electrodes        .     0-800  kg.      „  „  0-35       „ 

Labour    .          .     0-025  „  ,,  5  „ 

Electrical  energy        40  kw.  at  -006  fr.  per  kw. 

Total 


0-585  fr. 

0-075,, 

0-280,, 

0-125,, 

0-240,, 

l-305fr. 


per  kg.  of  aluminium  (i.e.  roughly  6d.  per  lb.),  to  which,  in  general,  transport 
charges  must  be  added. 

In  the  United  States  of  America,  the  cost  price  of  aluminium  in  1906 
would  be,  according  to  "The  Mineral  Industry,"  roughly  7£d.  per  lb.  The 
price  of  aluminium  has  varied  in  a  very  noticeable  manner  since  1855,  having 
passed  through  the  following  stages  : — 

Fr.  per  kg. 


1855  . 

1886  . 

1890  . 

1900  . 

1908  (end  of  Heroult  patents) 

1908-1914 

1916    . 


1230 

78 

19 

2-5 

2 

1-5-21 
6-8-7-0 


Price  per  lb. 
£22     5     3 
183 
6     10 
11 


£-9 
2/6-2/6| 


8  ALUMINIUM  AND  ITS  ALLOYS 

Aluminium  is  often  cast  into  billets,  frequently  cylinders  of 
3  kg.  in  weight,  80  cm.  high  and  4  cm.  in  diameter  (31-5  in.  X 
1  -57  in.).  The  slabs  or  billets  are  cast  from  a  mixture  of  ingots, 
and  therefore  a  fresh  analysis  must  be  carried  out  to  give  the 
quality. 

The  temperature  of  casting  is  usually  750-775°,  and  the 
temperature  of  rolling  400-450°,  roughly  the  temperature  of 
smouldering  wood. 

ROLLING  OF  ALUMINIUM  INTO  THIN  SHEETS.* 

Aluminium  can  be  rolled  into  sheets  '01  cm.  thick  (-0039  in.), 
similar  to  tinfoil.  The  process  has  been  carried  out  by  Drouilly 
— a  strip  initially  0-35  cm.  thick  (-138  in.)  is  rolled  in  the  cold 
to  0-04  cm.  (-016  in.);  the  reduction  is  made  in  six  passes 
with  intermediate  annealing.  The  second  stage  consists  in 
reducing  the  sheets  to  a  thickness  of  -01  cm.,  either  by  means 
of  blows  from  a  150  kg.  (roughly  3  cwt.)  pneumatic  hammer, 
giving  300  blows  per  minute,  or  by  further  rolling. 

EXTRUSION. 
Tubes  and  sections  can  be  obtained  by  extrusion.! 

ALUMINIUM  DUST. 

Powdered  aluminium,  in  the  form  of  paint,  is  applied  to 
finished  metallic  goods,  resulting  in  a  galvanisation  effect. 
For  literature  on  this  subject,  the  work  of  Guillet  (loc.  cit.) 
should  be  consulted. 

*  For  details  of  process,  see  Guillet,  "  Progres  des  Metallurgies  autreque 
la  Siderurgie  et  leur  Etat  actuel  en  France,"  pp.  264-268.  (Dunod  et  Pinat, 
1912.) 

t  Cf.  Breuil,  "  Genie  Civil,"  1917.    Nos.  23  and  24. 


CHAPTER  II 


WORLD'S   PRODUCTION 
I.    BAUXITE. 

THE  French  Minister  of  Commerce  gives  the  following  par- 
ticulars concerning  the  world's  production  of  bauxite  : — * 


U.S.A. 

France 

Great 

Britain 

Italy 

Tonnes 

Tons 

Tonnes 

Tons 

Tonnes 

Tons 

Tonnes 

Tons 

1910 
1911 
1912 
1913 

152,070 
158,107 
162,685 
213,605 

149,698 
155,610 
160,110 
210,228 

196,056 
254,831 
258,929 
309,294 

193,358 
250,800 
254,836 
304,410 

4,208 
5,103 
5,882 
6,153 

4,142 
5,022 
5,789 
6,056 

6,952 

6,842 

It  is  therefore  evident  that  up  to  1914,  there  were  only  two 
important  centres  in  the  world  for  the  production  of  bauxite, 
namely,  France  and  the  United  States  of  America. 
POSITION  IN  1913. 

The  distribution  of  bauxite  in  1913  (527,536  tons)  is  shown 
in  the  following  diagram  (Fig.  2) : — 


Scale 


10,000 
Tons 


O 


FIG.  2. — Distribution  of  Bauxite. 

"Vol.  I,  "Rapport  general  sur  I'industrie  francaise,  sa  situation,  son 
avenir,"  based  on  the  work  of  sections  of  the  "Comite  consultatif  des  Arts 
et  Manufactures  "  and  of  the  "Direction  des  Etudes  techniques,"  April,  1919. 
(Director:  M.  Guillet). 

9 


10 


ALUMINIUM  AND  ITS  ALLOYS 


Sixty -five  per  cent  of  the  French  production  was  exported, 
half  of  which  (i.e.  32  %)  was  sent  directly  or  indirectly  to 
Germany,  approximately  15  %  to  Great  Britain,  and  a  certain 
proportion  to  the  United  States,  which  is  rapidly  falling  off,  as 
the  new  beds  are  developed  in  that  country,  in  Tennessee  and 
North  Carolina. 

Of  the  7365  tons  (7483  tonnes)  of  alumina  exported,  80  % 
goes  to  supply  the  Swiss  factories. 

The  Report  of  the  French  Minister  of  Commerce  (loc.  cit.) 
shows  the  influence  of  the  war  on  the  production  of  bauxite. 

(a)  France. 


Bauxite  for 
Aluminium 

Bauxite  for 
other  purposes 

Total 

Tonnes 

Ton 

Tonnes 

Tons 

Tonnes 

Tons 

1915 
1916 
1917 

37,894 
68,866 
101,748 

37,296 
67,779 
100,150 

48,628 
37,334 
19,168 

47,860 
36,743 

18,865 

86,522 
106,200 
120,916 

85,156 
104,520 
119,015 

The  diminution  in  production  is  clearly  due  to  the  large  falling 
off  of  exports. 

(b)  United  States. 
1915 


293,253  tons  (297,961  tonnes)  of  bauxite. 


1916  . 

1917  . 

(c)  Great  Britain. 
1915     . 
1917 


418,640 
559,750 


(425,359 
(568,690 


11,726  tons  (11,914  tonnes)  of  bauxite. 
14,714       „    (14,950      „        ) 


The  whole  of  this  amount  was  imported  from  the  French  beds 
at  Var.  The  discovery  of  beds  in  British  Guiana,  where  there 
are  large  waterfalls,  will  probably  affect  the  British  production 
very  considerably. 

(d)  Italy. 

Position  unchanged. 

(e)  Germany. 

Germany  has  been  unable  to  import  French  bauxite,  and 
has,  therefore,  since  the  war,  begun  to  work  the  beds  at  Frank- 
fort-on-Main. 

(f)  Austria-Hungary. 

Austria-Hungary  has  supplied  the  needs  of  Germany  during 
the  war.  Just  when  war  was  declared,  very  important  beds 


WORLD'S  PRODUCTION 


11 


12  ALUMINIUM  AND  ITS  ALLOYS 

(20,000,000  tons)  were  discovered  in  Hungary  (Siebenbergen). 
The  bauxite  was  sent  to  Germany,  and  works  were  erected, 
on  the  spot,  for  treating  the  mineral.  In  addition,  there  are 
mines  in  Dalmatia,  Herzegovina,  Istria  and  Croatia,  which 
are  either  being  worked  or  are  ready  to  be  worked.  The  quality 
of  this  bauxite  seems  on  the  whole  very  inferior  to  that  of  the 
French. 

II.    ALUMINIUM. 

A  statement  of  production  figures  can  only  be  made  with 
caution,  discriminating  between  possible  and  actual  output. 
The  latter,  a  fraction  of  the  former,  depends  upon  the  demand, 
and  also  upon  the  possibility  of  obtaining  materials  for  the 
production  of  other  substances — for  instance,  the  manufacture 
of  aluminium  replacing  that  of  chlorates,  and  conversely. 

Statistics,  from  this  point  of  view,  are  often  lacking  in  clear- 
ness. Nevertheless,  bearing  in  mind  these  two  considerations, 
we  can  consider  the  following  figures  as  sufficiently  accurate, 
referring  to  an  average  annual  production. 

(a)  France. 

France,  as  is  shown  in  the  accompanying  map  (Fig.  3),  is 
favourably  situated  for  the  production  of  aluminium.  The 
close  proximity  of  the  bauxite  beds,  the  alumina  works,  and 
the  water  power  necessary  for  the  electro-metallurgy,  forms  a 
unique  combination,  and,  in  addition,  carbon  can  be  easily 
conveyed  to  the  works. 

Actual  output,  12,000-15,000  tons  per  annum. 
Possible  output,  18,000-20,000  tons  per  annum. 

ALUMINIUM  WORKS. 

The  French  works  are  amalgamated,  forming  "  L' Aluminium 
fran9aise,"  and  are  grouped  into  companies  : — 

(i)  The  "  Societe  Electro-metallurgique  fran9aise,"  with 
works  at  Praz,  and  at  St.  Michel  de  Maurienne  in  the  valley  of 
the  Arc,  and  at  Argentiere  in  the  valley  of  the  Durance. 

(ii)  The  "  Compagnie  des  Produits  chimiques  d'Alais  et  de 
la  Camargue,"  possessing  the  Calypso  works  (at  St.  Michel  de 
Maurienne),  and  works  at  St.  Jean  de  Maurienne  in  the  valley 
of  the  Arc. 

(iii)  The  "  Societe  d'Electro-chimie,"  works  at  Premont,  in 
the  valley  of  the  Arc. 

(iv)  "  La  Societe  Electro-chimique  des  Pyrenees,"  with  works 
at  Auzat  (Ariege). 


PLATE   I. 


PHOTOGRAPH  1. — NORWEGIAN  NITRIDES  AND  ALUMINIUM  COMPANY. 
Works  at  Eydehavn  near  Arendal  (25,000  H.P.),  situated  on  an  arm  of  the  sea. 


PHOTOGRAPH  2. — NORWEGIAN  NITRIDES  AND  ALUMINIUM   COMPANY. 
Works  at  Tyssedal  (35,000  H.P.)  on  the  Hardanger  Fjord. 

To  face  page  1 


PLATE    III. 


ENGINE-ROOM  AT  CALYPSO. 


To  face  page  13 


WORLD'S  PRODUCTION  13 

ALUMINA  WORKS. 

The  alumina  works  are  situated  near  the  bauxite  beds  in 
Herault,  Var,  and  Bouches-du-Rhone,  at  Gardanne  and  La 
Barasse  (Bouches-du-Rhone)  and  at  Salindres  (Gard). 

(b)  Great  Britain. 
Output  about  6000  tons. 

There  are  two  companies  : — 

(i)  The  British  Aluminium  Company  (Scotland  and  Norway), 
(ii)  The  Aluminium  Corporation  (works  at  Dolgarrog,  North 
Wales). 

(c)  Italy. 

Output  1500-2000  tons. 

(d)  Switzerland. 

Output  12,000-13,000  tons,  from  works  at  Neuhausen 
(canton  of  Schaffhausen)  and  at  Chippis  and  Martigny  (canton 
of  Valais).  It  is  noticeable  that  in  Switzerland  there  are  no 
works  for  the  preparation  of  alumina  from  bauxite,  hence  the 
materials  required  for  the  manufacture  of  aluminium,  alumina 
and  cryolite  are  imported. 

(e)  Nonuay. 

The  Norwegian  output  has  been : — 

1913     .         .     approximately   1000  tons 

1917  ...  „  7000     „ 

1918  .          .  „  6000     „ 

Its  possible  production  may  be  about  15,000-16,000  tons. 
Alumina  is  imported  mainly  from  the  works  at  Menessis 
(Somme)  and  Salzaete  (Belgium),  belonging  to  L'Aluminium 
fran9aise,  which  have  been  damaged  during  the  war. 

(f )  United  States  and  Canada. 

The  output  of  the  United  States  and  of  Canada  in  recent 
years  has  been  about  30,000  tons;  it  is  capable  of  great 
development,  but  it  is  difficult  to  give  precise  details  on  the 
subject. 

The  "  Rapport  sur  1'Industrie  frangaise  "  of  the  Minister 
of  Commerce  gives,  as  a  probable  figure  for  1917,  70,000  tons, 
which  might  rise  to  80,000  with  further  increase  in  prospect. 

The  two  large  American  companies  are  the  Aluminium 
Company  of  America,  and  the  Northern  Aluminium  Company 


14  ALUMINIUM  AND  ITS  ALLOYS 

of  Canada,   having  their  main  works  at  Niagara  Falls,   at 
Massena,  at  Quebec  and  at  Schawinigan  Falls  respectively. 

(g)  Germany  and  Austria. 

It  is  really  difficult  to  give  precise  returns  on  the  capacity 
for  production  of  these  two  countries.  It  has  been  given  as 
approximately  10,000  tons,  though  it  is  not  possible  actually 
to  verify  this  figure. 

In  conclusion,  the  following  table  of  actual  world's  production 
may  be  given,  omitting  all  more  or  less  hypothetical  specula- 
tions : — 

United  States  and  Canada      .          .  70,000  tons  (?) 

France 15,000  „ 

Switzerland           ....  12,000  „ 

Great  Britain        ....  6,000  „ 

Norway       .          .          .          .  6,000  „ 

Italy 2,000  „ 

Germany  and  Austria    .          .          .  10,000  „     (?) 


Total,  about         1 20,000  tons 


PART  II 
PROPERTIES  OF  ALUMINIUM 

CHAPTER  I 
PHYSICAL  PROPERTIES 

Density  :  2-6  (as  annealed),  2-7  (as  worked,  or  when  impurities 

(iron  and  copper)  are  present). 

This  places  aluminium  among  the  lightest  metals  (lead, 
11-4;  nickel,  8-94;  iron,  7-8;  tin,  7-3;  zinc,  7;  anti- 
mony, 6). 

Atomic  Weight :  26-9. 

Specific  Heat :    0-22,  increasing  with  rise  of  temperature.    It 
finally  reaches  0-308  at  about  the  melting  point. 

Thermal  Conductivity  :  36  (silver=100). 

Aluminium  is  a  substance,  therefore,  having  a  great  specific 
heat,  and  a  high  thermal  conductivity,  which  renders  it 
particularly  suitable  for  the  manufacture  of  cooking  utensils. 

Electrical  Conductivity  and  Resistance. 

The  electrical  conductivity  is  very  high,  being  about  60  % 
of  that  of  copper.  Its  specific  resistance  is  2-78  microhms  per 
centimetre  cube. 

Melting  Point :  about  650°. 


16 


CHAPTER  II 
ANALYSIS   AND   GRADING 

THE  division  of  aluminium  into  grades  is  based  upon  the 
amount  of  impurities  present.    The  chief  impurities  are  : — 

Group  I :  Iron  and  silicon. 

Group  II :    Carbides,   sulphides,   copper,   zinc,   tin,   sodium, 
nitrogen,  boron,  titanium. 

Group  III :  Alumina. 

The  electrodes,  in  particular  the  anodes,  form  the  principal 
source  of  the  impurities.  The  anodes  can  be  made  of  petroleum 
coke,  anthracite,  or  gas  carbon,  using  tar  as  a  binding  material. 
All  manufacturers  prefer  petroleum  coke,  which,  before  the 
war,  contained  1  %  of  ash,  and  during  the  war,  2-3  %.  The 
other  materials,  anthracite  and  gas  carbon,  contain  4-5  % 
of  ash. 

Group  I :  Iron  and  silicon. 

The  presence  of  more  than  1  %  of  iron  usually  causes  faulty 
castings  which  are  useless.  As  a  rule,  the  amount  of  silicon 
is  about  one-third  of  that  of  the  iron,  and  rarely  exceeds  one- 
half. 

Group  II :  Various  impurities,  other  than  alumina. 

These  impurities,  with  careful  working,  are  present  only  in 
relatively  small  quantities,  less  than  1  %,  but  their  estimation 
is  necessary,  since,  owing  to  some  accident  during  the  working, 
they  may  attain  abnormal  proportions. 

Group  III :  Alumina. 

It  is  impossible  to  emphasise  too  much  the  importance  of 
this  impurity.  For  a  long  time,  it  was  customary  to  estimate 
the  iron,  silicon  and  other  impurities,  and,  ignoring  the 
alumina,  to  determine  the  aluminium  by  difference.  This 
method,  in  which  alumina  is  returned  as  metallic  aluminium, 
is  unsatisfactory,  for  experience  has  shown  that  excessive 

16 


ANALYSIS  AND  GRADING  17 

quantities  of  alumina  are  very  harmful  on  account  of  its 
infusibility  at  casting  temperatures,*  its  higher  density,! 
and  its  insolubility  in  the  molten  metal. 

This  impurity  must  therefore  be  estimated.  Furthermore, 
a  high  percentage  of  alumina  seems  to  favour  the  formation  of 
blow-holes.  For  these  reasons,  the  melting  up  of  aluminium 
scrap,  more  or  less  oxidised,  gives  poor  results. 

GRADES  OF  ALUMINIUM. 

As  already  stated,  the  usual  industrial  practice  is  to  estimate 
only  iron  and  silicon,  the  aluminium  content  being  determined 
by  difference — this  obviously  gives  a  fictitious  value. 

Grade  I :  Aluminium  nominally  99-5  %.  i.e.  the  total  amount 
of  iron  and  silicon  being  equal  to  or  less  than  0-5  %. 

Grade  II :  Aluminium  nominally  99-0  %.  i.e.  the  total 
amount  of  iron  and  silicon  being  equal  to  or  less  than 
1-0  %. 

Grade  III :  Aluminium  nominally  98-99  %.  i.e.  the  total 
amount  of  iron  and  silicon  being  equal  to  or  less  than  2  %. 

Though  retaining  this  long-established  system  of  classifica- 
tion, the  foregoing  grading  should  be  modified,  so  as  to  take 
into  account  the  impurities  of  the  second  group  as  well  as 
those  of  the  first,  still,  however,  ignoring  the  alumina. 

We  then  have  the  following  grades  : — J 

Grade  I :  Aluminium  content  (by  difference)  99-5  %  or  over. 
Grade  II :  Aluminium  99-99-5  %. 

Grade  III :  Aluminium  98-99  %. 

In  the  first  two  grades,  the  impurities  of  the  second  group 
(carbides,  sulphides,  copper,  zinc,  tin,  sodium,  nitrogen, 
boron,  and  titanium)  should  not  exceed  0-3  %  ;  in  the  third 
grade  these  impurities  should  not  exceed  0-4  %,  the  iron  1  %, 
and  the  silicon  0-6  %. 

Alumina  is  not  considered  in  calculating  the  purity,  but 
should  not  exceed  0-4  %  for  Grade  I,  0-6  %  for  Grade  II, 
and  0-8  %  for  Grade  III.  These  are  safe  limits  to  allow, 
without  interfering  with,  or  reducing,  the  production. 

*  Melting  point  of  alumina  3,000°  C.,  of  aluminium  650°  C. 

t  Density  of  alumina  3-75,  of  aluminium  2-6. 

j  This  system  of  grading  is  adopted  in  the  French  Aeronautical  Specifica- 
tions, and  the  analytical  methods  are  given  in  Appendix  I.    A  variation  of 
0-25  %  in  the  aluminium  content  is  allowed  in  Grade  I,  0-50  %  in  Grade  II, 
and  0-75  %  in  Grade  III. 
C 


CHAPTER  III 
MECHANICAL   PROPERTIES 

THE  mechanical  properties  can  be  grouped  as  follows  : — 

A.  Tensile  Properties:   Tensile  Strength,  Elastic  Limit,  and 
Elongation. 

B.  Hardness  and  Shock  Resistance. 

C.  Cupping  Value  :  Depth  of  Impression  and  Breaking  Load. 

Tests  have  been  carried  out  on  metal  of  varying  thickness, 
as  shown  below  : — 

0-5  mm.  sheet :  Tensile  and  Cupping  Tests. 

2  mm.  sheet :  Tensile,  Cupping,  and  Hardness  (scleroscope) 

Tests. 
10  mm.  sheet :  Tensile,  Shock,  and  Hardness  Tests. 

The  variations  in  these  properties  with 
(i)  different  amounts  of  cold  work ; 

(ii)  different  anneals  subsequent  to  varying  degrees  of  work, 
have  been  investigated.  An  account  of  the  experiments  and 
results  will  be  given  in  the  following  form  : — 

A.  TENSILE  PROPERTIES. 

(i)  Variation  in  tensile  properties  with  the  amount  of  cold 
work. 

(a)  Thin  test  pieces. 

(b)  Thick  test  pieces. 
Discussion  of  Results. 

(ii)  Variation  in  tensile  properties  with  increasing  annealing 
temperature,  following  varying  amounts  of  cold  work. 

(a)  Thin  test  pieces. 

(b)  Thick  test  pieces. 
Discussion  of  results. 

B.  HARDNESS  AND  SHOCK  RESISTANCE. 

(i)  Variation  of  these  properties  (Brinell  Hardness  and 
Shock  Resistance)  with  amount  of  cold  work,  using  test  pieces 

18 


MECHANICAL  PROPERTIES         19 

of  10  mm.  thick  sheet,  and  variation  of  Scleroscope  Hardness 
with  the  amount  of  cold  work  for  sheets  of  the  thin  series. 
Discussion  of  results. 

(ii)  Variation  of  Brinell  Hardness  and  Shock  Resistance 
with  increasing  annealing  temperature,  after  varying  amounts 
of  cold  work,  using  test  pieces  from  sheets  10  mm.  thick  (thick 
series). 

Discussion  of  results. 

C.  CUPPING  VALUE. 

Depth  of  impression  and  breaking  load,  using  test  pieces  of 
metal  comprising  the  thin  series  only. 

(i)  Variation  of  these  properties  with  amount  of  cold  work. 

(ii)  Variation  of  these  properties  with  increasing  annealing 
temperature  following  varying  amounts  of  cold  work. 
Discussion  of  results. 

D.  FINAL  SUMMARY. 

E.  CONTEMPORARY  LITERATURE  ON  THE  SUBJECT. 

A.    TENSILE  PROPERTIES 

Thin  Series 

Dimensions  of  test  pieces. 

TYPE  IA.  (Length  100mm. 

Between  shoulders  |  Breadth  20  mm. 

(Thickness  0-5  mm. 
Area  of  cross  section  10  sq.  mm.* 
Gauge  length  (for  measuring  elongation)  =  \/66  -67s 

=  30  mm. 

TYPE  IB.  [Length  100  mm. 

Between  shoulders   -[  Breadth  20  mm. 
[Thickness  1  mm. 
Area  of  cross  section  20  sq.  mm. 


Gauge  length  =  V^G-GTs^SG  mm. 

TYPE  Ic.  [Length  100  mm. 

Between  shoulders  -j  Breadth  20  mm. 

'Thickness  1-5  mm. 
Area  of  cross  section  30  sq.  mm. 
Gauge  length  =  V66'67s=45  mm. 

*  These  values  are  only  approximate.  In  each  case  the  breadth  and 
thickness  were  measured  to  the  nearest  -01  mm.,  and  the  exact  cross  section 
calculated  from  these  figures. 


20  ALUMINIUM  AND  ITS  ALLOYS 

TYPE  ID.  (Length  100  mm. 

Between  shoulders  -I  Breadth  20  mm. 
[Thickness  2  mm. 
Area  of  cross  section  40  sq.  mm. 
Gauge  length  =  V66-67s=50  mm. 

Thick  Series 

TYPE  II.  [Length  100mm. 

Between  shoulders  J  Breadth  15mm. 

[Thickness  10  mm. 
Area  of  cross  section  150  sq.  mm. 
Gauge  length=V66-67s=100  mm. 

TESTING  LABORATORIES. 

The  experiments  on  the  variation  of  mechanical  properties 
with  cold  work  (thin  series)  and  the  cupping  tests  (both  in  the 
worked  and  annealed  states)  were  carried  out  at  the  "  Chalais 
Meudon "  Laboratory.  The  experiments  on  the  effect  of 
annealing  at  different  temperatures  after  cold  work  were 
carried  out  at  the  Conservatoire  des  Arts  et  Metiers.  Reports 
of  the  latter  experiments  are  given  in  the  appendices. 

I.   Variation  of  the  Tensile  Properties  (Tensile  Strength,  Elastic 
Limit,  and  Elongation)  with  the  amount  of  cold  work. 

DEFINITION  OF  COLD  WORK. 

A  metal,  which,  as  the  result  of  work  "  in  the  cold,"  i.e.  at 
relatively  low  temperatures,  has  undergone  permanent  defor- 
mation, is  said  to  be  "  cold  worked  "  or  "  work  hardened." 
The  properties  of  the  metal,  thus  treated,  are  changed,  and 
the  amount  of  this  change  is  a  measure  of  the  cause — the 
so-called  cold  work.  A  metal  which  has  been  completely 
annealed  has,  by  definition,  zero  cold-work. 

If  S  be  the  initial  section  of  a  bar  in  the  annealed  state  and 
if  s  be  the  final  section  after  cold  work  (drawing  or  rolling), 
the  cold  work  may  be  defined  in  terms  of  the  deformation  as 
follows : — 

*    Cold  work     S  (initial)— s(final) 


;%)  s(final) 


xioo. 


As  has  been  pointed  out  in  the  author's  work  on  "  Copper 
and  Cartridge  Brass,"  the  "  percentage  cold  work  "  given  by 
the  above  formula  is  a  function  of  the  deformation  only,  and 
does  not  give  any  indication  of  the  value  of  the  mechanical 


MECHANICAL  PROPERTIES  21 

properties.  The  latter  may  actually  remain  stationary,  while 
the  percentage  of  deformation  continues  to  increase  with  the 
deformation  itself.  We  can  therefore  distinguish  two  values  : — 

(a)  The  cold  work  in  terms  of   deformation  (theoretical 

cold  work). 
(6)  The  cold  work  in  terms  of  the  change  in  mechanical 

properties  (effective  cold  work). 

In  this  book,  unless  otherwise  stated,  it  is  always  the  former 
that  is  meant,  and  this  allows  of  easy  evaluation  in  course  of 
manufacture. 

(a)  Thin  Series 

The  tests  on  the  thin  series  were  carried  out  on  test  pieces 
cut  respectively  from  sheets  of  the  thicknesses  specified  :— 

Type  la  .  .  Thickness  0-5  mm. 

„     16  .  .  „         1-0  mm. 

„     Ic  .  .  „         1-5  mm. 

„     Id  .  „         2-0  mm. 

Sheets  of  each  of  the  above  thicknesses  were  subjected  to 
the  following  amounts  of  cold  work,  and  the  results  investigated. 

Cold  work     0  %  Ratio  S/s  0      (completely  annealed) 
50%  „      1-5 

100%  „      2 

300  %  „      4 

Method  of  working  sheets  and  slabs  so  as  to  obtain  required 
amounts  of  cold  work. 

Two  methods  were  employed  in  the  preliminary  working 
of  the  sheets  and  slabs. 

FIRST  METHOD. 

Annealed  Metal.  A  slab  40  mm.  thick  at  an  initial  tempera- 
ture of  450°  is  reduced  to  the  required  thickness  by  hot  rolling, 
without  intermediate  reheating,  and  is  finally  annealed  at 
350°. 

Cold-Worked  Metal.  Assuming  that  100  %  cold  work  is 
desired,  a  sheet  40  mm.  thick  is  reduced  by  hot  rolling,  without 
intermediate  reheating,  to  double  the  final  thickness  required. 
It  is  then  annealed  at  350°,  and  cold  rolled  so  as  to  reduce 
the  section  by  one-half.  A  similar  process  is  employed  for 
the  other  degrees  of  cold  work  investigated. 


22  ALUMINIUM  AND  ITS  ALLOYS 

SECOND  METHOD. 

A  slab  40  mm.  thick,  at  an  initial  temperature  of  450°,  is 
reduced  to  a  uniform  thickness  of  8  mm.  by  hot  rolling. 

Annealed  Metal.  The  sheet,  8  mm.  thick,  is  reduced  to  the 
required  thickness  by  cold  rolling,  with  intermediate  annealing 
at  350°  every  2  mm.  reduction,  and  is  finally  annealed  at  350°. 

Cold-Worked  Metal.  Assuming  that  100  %  cold  work  is 
desired,  the  sheet,  8  mm.  thick,  is  reduced  by  cold  rolling, 
with  intermediate  annealing  every  2  mm.  reduction,  to  double 
the  final  thickness  required.  It  is  then  annealed  at  350°,  and 
cold  rolled  so  as  to  reduce  the  section  by  one-half.  A  similar 
process  is  employed  for  the  other  degrees  of  cold  work  in- 
vestigated. 

A  comparative  study  of  the  cold  working  of  thin  sheets 
was  carried  out  by  both  these  methods,  wrhereas  in  the  study 
of  the  cold  working  of  thick  sheets,  and  in  the  study  of  annealing 
alone,  the  second  method  only  was  employed.  Although  the 
second  method  is  more  uniform  and  more  sound,  it  has  not 
given  results  superior  to  those  of  the  first. 

As  will  be  seen  below,  it  seems  as  if,  up  to  a  certain  limit, 
large  amounts  of  cold  work  need  not  be  avoided  in  manufacture, 
provided  that  this  is  only  an  intermediate  stage,  and  is  followed 
by  a  re-softening  anneal. 

ANALYSIS 

Cold  work  0  % 

Thickness  0-5  mm.     1mm.  1-5  mm.  2mm. 

Iron          .          .     0-93%       0-82%  0-98%  0-95% 

Silicon      .          .     0-56  0-52  0-56  0-45 

Cold  work  50  % 

Iron          .          .     0-88  0-84  0-97  0-93 

Silicon      .          .     0-25  0-26  0-39  0-41 

Alumina  .          .     0-36  0-30  0-26  0-34 

Cold  work  100  % 

Iron          .          .     0-81            0-83  0-70  0-81 

Silicon      .          .     0-32            0-38  0-23  0-23 

Alumina  .          .     0-24           0-29  0-26  0-24 

Cold  work  300  % 

Iron          .          .     0-88            0-77  0-85  0-72 

Silicon      .          .     0-31            0-46  0-56  0-46 

Alumina  .               0-17           0-16  0-24  0-22 


MECHANICAL  PROPERTIES 


23 


NUMBER  OF  TESTS. 

For  each  degree  of  cold  work,  two  sheets  were  used  for  the 
tensile  tests,  and  in  each  sheet  three  test  pieces  were  cut 
longitudinally  and  three  transversely. 


THIN  SERIES 
(Sheet  1mm.  thick) 


-13 


50 


100  150  200 

Cold     Work 


250 


FIG.  4. — Variation  in  Mechanical  (tensile)  Properties  with 
Cold  Work. 

RESULTS  OF  TESTS. 

Fig.  4  summarises  the  results  for  test  pieces  of  the  Type  Ib 
(I  mm.  thickness)  cut  longitudinally. 

After  discussing  the  results  obtained  for  this  type,  we  will 
point  out  the  variations  observed,  due  to  the  different  thick- 
nesses of  the  sheets  comprising  the  thin  series,  and  to  the 


24  ALUMINIUM  AND  ITS  ALLOYS 

direction,  longitudinal  or  transverse,  in  which  the  test  pieces 
were  cut. 

Cold  work  0  %  (annealed  state) : — 

Elastic  Limit :  4-5  kg.  per  sq.  mm.  (2-86  tons  per  sq.  in.). 

Tensile  Strength  :  9-0  kg.  per  sq.  mm.  (5-72  tons  per  sq.  in.). 

Elongation :    40  %. 

Cold  work  50  %  :— 

Elastic  Limit :  12-0  kg.  per  sq.  mm.  (7-62  tons  per  sq.  in.). 
Tensile  Strength  :  14-0  kg.  per  sq.  mm.  (9-09  tons  per  sq.  in.) 
Elongation:  11%. 

Cold  work  100  %  :- 

Elastic  Limit :  14-0  kg.  per  sq.  mm.  (8-89  tons  per  sq.  in.). 
Tensile  Strength  :  15-0  kg.  per  sq.  mm.  (9-52  tons  per  sq.  in.) 
Elongation :  9  %. 

Cold  work  300  %  :- 

Elastic  Limit :  17-5  kg.  per  sq.  mm.  (11-11  tons  per  sq.  in.). 
Tensile  Strength:  18-0  kg.  per  sq.  mm.  (1 1  -43  tons  per  sq.  in.). 
Elongation  :  6  %. 

(i)  Merely  cold  working  to  the  extent  of  50  %  has  completely 
changed  the  properties  of  aluminium,  and  the  Elongation  has 
been  reduced  to  a  quarter  of  its  original  value.  Consequently, 
if  work  hardening  is  undesirable,  even  a  very  small  amount  of 
deformation  must  be  avoided,  since  the  changes  in  the 
properties  take  place  very  markedly  from  the  outset. 

(ii)  The  maximum  cold  work,  beyond  which  deterioration 
and  disintegration  may  set  in,  is  reached  when  the  Tensile 
Strength  is  approximately  doubled. 

(iii)  If  cold  work  be  expressed,  no  longer  in  terms  of  the 
deformation,  but  in  terms  of  the  changes  in  the  properties,  then, 
choosing  as  variable  the  Tensile  Strength,  and  employing  the 
formula 

Cold  work=—    -  where  R= Tensile  Strength 

(cold  worked) 
r= Tensile  Strength 
(annealed) 

we  have,  in  the  case  of  the  thin  series,  the  following  results  : — 
Cold  work  (deformation)  0  %  Cold  wrork  (effective)  0 

3>  5J  ^O      /Q  ,,  ,,  -3 

100%  „  „  f 

300%  „  „  1 


MECHANICAL  PROPERTIES  25 

It  seems,  therefore,  that  200-300  %  cold  work  is  the  maximum 
for  the  working  of  aluminium,  giving  what  might  be  called  the 
"  Maximum  Effective  Cold  Work." 

INFLUENCE  OF  THICKNESS  (THIN  SERIES). 

The  variation  in  thickness  between  0-5  mm.  and  2-0  mm. 
exerts  only  a  slight  effect  on  the  results,  so  that  the  mean 
curve  given  for  test  pieces  of  1-mm.  thickness  may  be  taken 
as  the  curve  for  all  the  thin  series. 

EFFECT  ON  TENSILE  PROPERTIES  OF  THE  DIRECTION  IN  WHICH 

TEST  PIECES  WERE  CUT. 

The  Elongation  in  the  transverse  test  pieces  is  less  than  that 
in  the  longitudinal. 

Cold  work  0  %  Difference  10  % 

Cold  work  50  %  and  above      Maximum  difference  40  % 

In  the  Tensile  Strength  and  Elastic  Limit  there  is  practically 
no  difference. 

(b)  Thick  Series 

The  tests  on  the  "  Thick  Series  "  have  been  carried  out  on 
test  pieces  of  Type  II,  thickness  10  mm.,  cut  from  sheets  of 
this  thickness. 

The  following  different  amounts  of  cold  work  were  investi- 
gated : — 

Cold  work  0  %       Ratio  :    ^litifQSection=  0    (completely 

Final  Section  annealed) 

50%  „  1-5 

M       100%  „  2 

»       300%  „  4 

ANALYSIS. 

Cold  work  0  %  :— 

Aluminium  .         .         .  99-00  % 

Iron 0-64  % 

Silicon  ....  0-33  % 

Carbon  .          .          .          .  0-03  % 

Alumina  ....  traces. 

Cold  work  50%:— 

Aluminium    .          .          .          .     98-80  % 

Iron 0-72  % 

Silicon  ....       0-35  % 

Carbon  .          .          .          .0-08  % 

Alumina        .         .         .  traces. 


26 


ALUMINIUM  AND  ITS  ALLOYS 


Cold  work  WO  %:— 

Aluminium 
Iron   . 
Silicon 
Carbon 
Alumina 


98-60  % 
0-84  % 
0-41  % 
0-07  % 

traces. 


THICK  SERIES 
(Longitudinal  ) 


40 


250 


300% 


100  150          200 

Cold     Work 
FIG  5. — Variation  in  Mechanical  Properties  with  Cold  Work. 

Cold  work  300  %  :— 

Aluminium   ....     99-01% 

Iron 0-61  % 

Silicon  ....       0-33  % 

Carbon  .          .          .          .0-03  % 

Alumina  traces. 


MECHANICAL  PROPERTIES 


27 


Figs.  5  and  6  summarise  the  variations  in  properties  in  the 
case  of  the  thick  series  (sheets  10  mm.  thick).* 

FIG.  5.    TESTS  ON  LONGITUDINAL  TEST  PIECES. 

As  can  be  seen,  the  variations  in  the  properties  with  cold 
work  (deformation)  are  similar  to  those  of  the  thin  series. 


THICK  SERIES 
(Transverse) 


II 


50 


250 


100  150  200 

Cold    Work 
FIG.  6. — Variation  in  Mechanical  Properties  with  Cold  Work. 

In  every  case  the  minima  and  maxima  are  approximately  the 
same. 

Tensile  Strength.    Minimum,     10  kg.  per  sq.  mm.  (6-35  tons 

per  sq.  in.). 

Maximum,    16  kg.  per  sq.  mm.  (10-16  tons 
per  sq.  in.). 

*  Cf.  Appendix  III.     Report  of  the  Conservatoire  des  Arts  et  Metiers. 
No.  13456,  February  5th,  1919. 


28 


ALUMINIUM  AND  ITS  ALLOYS 


Elongation.    Minimum,  8  %.     Maximum,  38  %. 

In  the  case  of  aluminium  in  thin  sheets  as  compared  with 
thick, 

(i)  The  cold  work,  whatever  its  amount,  is  more  homogeneous 
throughout  the  thickness. 

(ii)  The  effect  of  annealing  is  more  complete. 

THIN    SERIES 
(Test  Pieces  0.5  mm.  thick) 


100 


200  300  400 

Temperature 


500          600°C 


FIG.  7. — Variation  in  Mechanical  Properties  on  Annealing  at 
different  Temperatures  after  50  %  Cold  Work. 

FIG.  6.    TESTS  ON  TRANSVERSE  TEST  PIECES. 

The  Tensile  Strength  and  Elastic  Limit  are  little  affected  by 
the  direction  in  which  the  test  pieces  are  cut,  but,  on  the  other 
hand,  the  Elongation  undergoes  variations  of  the  order  of 
15  to  20  %. 


MECHANICAL  PROPERTIES 


29 


II.    Variation  of  Tensile  Properties  with  increasing  Annealing 
Temperature  following  varying  amounts  of  Cold  Work. 

(a)  Thin  Series 

EXPERIMENTAL  DETAILS  OF  THE  TESTS. 

••' 
The  tests  were  carried  out  on  two  series  of  tensile  test  pieces 

from  sheets  of  aluminium,  the  one  0-5  mm.  thick,  Type  la, 


THIN  SERIES 
(Test  Pieces  O'Smm.  thick) 


100 


200  300          400 

Temperature 


500          600  °C 


FIG.   8. — Variation  in  Mechanical  Properties  on  Annealing 
at  different  Temperatures  after  100  %  Cold  Work. 


the  other,   2-0  mm.  thick,  Type  Id.     Each   of  these  series 
includes  metal  in  three  degrees  of   cold  work,  50,   100,  and  . 
300  %. 


30 


ALUMINIUM  AND  ITS  ALLOYS 


INVESTIGATION  OF  THE   DURATION  OF  TIME  NECESSARY  FOR 
COMPLETE  ANNEAL  AT  VARIOUS  TEMPERATURES. 

Preliminary  tests  have  been  carried  out  with  a  view  to 
determining  the  minimum  time  necessary  to  give  the  properties 
characterising  each  temperature.* 


Kg.  per 


THIN  SERIES 
(Test  Pieces  O'Smm. thick) 


11 


40 


100 


500 


eoc 


200          300          400 
Temperature 

FIG.  9. — Variation  in  Mechanical  Properties  on  Annealing 
at  different  Temperatures  after  300  %  Cold  Work. 

The  following  results  were  obtained  for  the  two  series  : — 

Bath  Temperature  Duration  of  Time 

Oil  ...  100°— 150°— 200°— 250°— 300°  5  minutes. 
Sodium  nitrite  .  350°— 400°— 450°— 500°  3  minutes. 
Potassium  nitrate  .  550° — 600°  1  minute. 

*  Cf.  Appendix  IV.     Report  of  the  Conservatoire  des  Arts  et  Metiers. 
No.  13357,  January  24th,  1919. 


MECHANICAL  PROPERTIES 


31 


TEST  PIECES  0-5  mm.  THICK.    TYPE  IA. 

Figs.  7,  8,  and  9  summarise  the  results  obtained. 

STAGES  or  ANNEALING. 

Whatever  the  amount  of  work,  the  following  stages  can  be 
distinguished : — 

(i)  Region  of  cold  work, 
(ii)  Region  of  softening, 
(iii)  Region  of  complete  anneal, 
(iv)  Region  of  falling-off  of  Elongation. 

THIN  SERIES 

(Test  pieces  2mm.thick) 

11 


10 


100 


500 


600  °C 


200  300  400 

Temperature 

FIG.  10. — Variation  in  Mechanical  Properties  on  Annealing 
after  50  %  Cold  Work. 

(i)  Region  of  Cold  Work  ;  0-150°. 

W  ithin  this  range,  the  properties  remain  similar  to  those 
which  the  metal  possesses  in  the  particular  cold-worked  state, 


32 


ALUMINIUM  AND  ITS  ALLOYS 


as  given  in  Fig.  4.    The  effect  of  temperatures  up  to  150°  is 
therefore  insignificant. 

(ii)  Region  of  Softening  ;   150-350°. 

This  is  a  transition  stage,  in  which  the  aluminium  becomes 
softer,  and  gradually  acquires  the  properties  of  completely 
annealed  metal. 

THIN  SERIES 

(Teot  Pieces  2mm.  thick) 


100 


200  300  400 

Temperature 


500          600  °C 


FIG.  11. — Variation  in  Mechanical  Properties  on  Annealing 
after  100  %  Cold  Work. 

(iii)  Region  of  Complete  Anneal  ;   350-450°. 

This  is  the  region  in  which  the  extent  of  anneal  remains 
approximately  constant ;  that  is  to  say,  in  which  the  properties 
of  the  metal  are  almost  the  same  after  annealing  at  any  tempera- 
ture within  this  range. 


MECHANICAL  PROPERTIES 


33 


350°  to  450°  is,  therefore,  the  optimum  annealing  range  of 
temperature. 

(iv)  Region  of  Falling-off  of  Elongation  ;   450-500°. 

In  this  region  there  is  a  decrease  in  the  Elongation,  without 
any  appreciable  change  in  the  Tensile  Strength  and  Elastic 
Limit. 

THIN  SERIES 
(Test  Pieces  2mm.  thick) 


100 


500         600°C 


200  300  400 

Temperature 

Fio.  12. — Variation  in  Mechanical  Properties  on  Annealing 
after  300  %  Cold  Work. 

NOTES  ON  THE  RESULTS. 

(i)  The  softening  is  the  more  abrupt  as  the  original  cold 
work  increases. 

(ii)  The 'temperature  of  complete  anneal  (characterised  by 
maximum  elongation)  becomes  lower  as  the  cold  work  increases. 
D 


34 


ALUMINIUM  AND  ITS  ALLOYS 


Amount  of  Original  Cold  Work 
50  %        . 
100  %        . 
300  % 


Temperature  of  Maximum 

Elongation 

425° 

400° 

350° 


(iii)  The  values  of  the  properties  in  the  completely  annealed 
state  increase  with  the  amount  of  original  cold  work,  up  to 
300  %. 


Amount  of 
Cold  Work 

Tensile  Strength 

Elastic  Limit 

%  . 
Elongation 

Kg.  /mm.  a     Tons  /in.  z 

Kg.  /mm.  2   Tons  /in.  2 

50% 
100  % 
300  % 

10-8                 6-8G 
11-0                6-99 
11-2                7-11 

4-8                3-05 
4-5                2-86 
5-2                3-31 

34-0 
37-5 
40-0 

This  shows  that,  in  the  treatment  of  aluminium,  it  is  advisable 
to  employ  extensive  cold  work,  up  to  a  maximum  amount 
varying  between  200  %  and  300  %,  always  provided  that  the 
work  is  followed  by  an  anreal  adequate  in  duration  and  at 
a  suitable  temperature. 

Large  amounts  of  cold  work — 

(i)  lower  the  length  of  time  necessary  for  complete  anneal, 
(ii)  lower  the  temperature  of  complete  anneal, 
(iii)  improve  the  properties. 

TEST  PIECES  2  mm.  THICK.    TYPE  ID. 

Figs.  10, 1 1,  and  12  summarise  the  results.  The  same  regions 
are  noticeable  as  in  Figs.  7,  8,  and  9,  and  lie,  approximately, 
within  the  same  limits  of  temperature,  and  the  same  remarks 
may  be  made  as  to  the  results  obtained  after  varying  cold  work. 

(b)  Thick  Series 
EXPERIMENTAL  DETAILS  OF  TESTS. 

Tests  were  carried  out  on  test  pieces  (Type  No.  II,  10  mm. 
thick)  taken  from  sheets  of  that  thickness  having  been  cold 
worked  to  the  extent  of  100  and  300  %. 

INVESTIGATION  or  THE  DURATION  or  TIME  NECESSARY  FOR 
COMPLETE  ANNEAL  AT  VARIOUS  TEMPERATURES. 

As  in  the  case  of  the  thin  test  pieces,  preliminary  tests  were 
carried  out  with  a  view  to  determining  the  time  required  to 
give  the  properties  characterising  each  temperature.* 

*  Of.  Appendix  V.  Report  of  the  Conservatoire  dee  Arts  et  Metiers. 
No.  13463. 


MECHANICAL  PROPERTIES 

The  results  are  as  follows : — 

Bath 


oil  . 

Sodium  nitrite   . 
Potassium  nitrate 


Temperature 
100-125-150-175-200-225-250° 
275-300-325-350-375-400-^25-450° 
475-500-525-550-575-600° 


35 


Duration  of 

Time 

6  minutes. 
4 
2 


Figs.   13  and  14  summarise  the  variations  in  mechanical 
properties  for  the  thick  series  (sheets  10  mm.  thick). 

THICK  SERIES 


100 


200         300          400 
Temperature 


500 


600°C 


FIG.  13. — Variation  in  Mechanical  Properties  on 
after  100  %  Cold  Work. 

FIGS.  13  (100  %  COLD  WORK)  AND  14  (300  %  COLD  WORK). 

As  in  the  case  of  the  thin  series,  the  same  regions  are  notice- 
able, and  a  comparison  of  the  two  figures  leads  to  the  same 
conclusions  as  to  the  effect  of  initial  cold  work  on  the  results 
obtained  after  a  subsequent  anneal. 


36 


ALUMINIUM  AND  ITS  ALLOYS 


B.    HARDNESS  AND  SHOCK  RESISTANCE 

I.  Variation  of  the  Brinell  Hardness  and  Shock  Resistance  with 
the  amount  of  cold  work,  using  test  pieces  taken  from 
sheets  10  mm.  thick,  and  of  the  Shore  scleroscope  hardness, 
with  the  amount  of  cold  work,  for  sheets  of  the  thin  series. 

HARDNESS  TESTS. 

(a)  Brinell  Tests  on  thick  sheets. 

These  were  carried  out  under  a  load  of  500  kg.  and  1000  kg. 
respectively,  using  a  ball  10  mm.  in  diameter.  The  results  are 
shown  in  Fig.  15. 

THICK  SERIES 
(Test  Pieces  1 0mm.  thick) 


0  160  200  300  400  500  600*C 

Temperature 

FlQ.  14, — Variation  in  Mechanical  Properties  on  Annealing 
after  300  %  Cold  Work.] 


MECHANICAL  PROPERTIES 


37 


As  is  evident  from  a  comparison  of  Fig.  15  and  Fig.  5,  the 
curves  of  Tensile  Strength  and  Elastic  Limit  plotted  against 
cold  work  are  of  the  same  general  form  as  the  hardness  curves 


42 

4 
40 

Shock 
39  Resistanc 

38 

37 

36 
35 
34 


2 

.§33 


•£  30 

m 

29 
28 
27 
26 
25 
24 
23 
22 
21 
20 


THICK  SERIES 

Brine!/ 



'Hardness 


Shock  Resistance 

(transuerse 


50 


100 


1 50          200 

Cold  Work 


250         300% 


FIG.  15. — Variation  in  Mechanical  Properties  (Hardness 
and  Shock)  with  Cold  Work. 

under  500  kg.  and  1000  kg.  These  hardness  curves  under 
500  and  1000  kg.  deviate  very  little  from  each  other,  and  the 
divergences,  for  which  experimental  errors  are  partly  re- 
sponsible, need  no  comment. 


38  ALUMINIUM  AND  ITS  ALLOYS 

Annealed  aluminium  possesses  a  Brinell  Hardness  of  23 
under  500  or  1000  kg.,  corresponding  with  a  Tensile  Strength 
of  approximately  10  kg.  per  sq.  mm.  (6-35  tons  per  sq.  in.). 
In  the  case  of  the  thick  series,  the  maximum  hardness,  as  also 
the  maximum  Tensile  Strength,  occurs  at  200  %  cold  work. 

(b)  Shore  Scleroscope  Tests  on  thin  sheets. 

As  ball  tests  are  impossible  on  thin  sheet,  rebound  tests 
were  made,  using  the  Shore  apparatus,  on  sheets  of  the  thin 
series,  possessing  respectively  50  %,  100  %,  and  300  %  cold 
work. 

The  average  scleroscope  numbers  of  sheets  1  and  2  mm.  thick 
are  as  follows  : — 

Average  scleroscope  number 
Test  pieces  1  mm.  thick         2  mm.  thick 

As  annealed    .  .  4-5  5-5 

50  %  cold  work  .  16-0  11-5 

100%  cold  work  .  24-0  14-0 

300  %  cold  work  .  28-0  16-0 

The  scleroscope  numbers  vary  with  the  thickness,  but, 
whatever  the  thickness,  the  scleroscope  number  of  completely 
annealed  metal  varies  between  4  and  6,  providing,  therefore, 
a  convenient  means  of  verifying  the  extent  of  anneal. 

SHOCK  TESTS. 

These  were  carried  out  on  test  bars,  55  x  10  x  10  mm.,  with 
a  Mesnager  notch  of  2  mm.  depth,  using  a  30  kg.  m.  charpy 
pendulum  of  the  Conservatoire  des  Arts  et  Metiers. 

The  results  are  also  shown  in  Fig.  15.  If  the  Shock  Resistance 
curves  (longitudinal  and  transverse)  of  Fig.  15  be  compared 
with  the  Elongation  curves  of  Figs.  5  and  6,  it  will  be  seen  that 
they  are  of  identical  shape. 

At  50  %  cold  work,  the  Shock  Resistance  reaches  almost  its 
minimum  value.  In  the  annealed  state,  the  Shock  Resistance 
varies  between  8  and  8-5  kilogramme-metres  per  sq.  cm., 
without  any  appreciable  difference  between  test  pieces  cut 
longitudinally  or  transversely.  This  difference,  however, 
becomes  more  marked  as  the  cold  work  increases. 

Minimum  Shock  Resistance,  300  %  cold  work  (longitudinal) 
5  kg.  m.  per  sq.  cm. 

Minimum  Shock  Resistance,  300  %    cold  work   (transverse) 
3  kg.  m.  per  sq.  cm. 

• 


MECHANICAL  PROPERTIES 


39 


II.  Variation  of  Brinell  Hardness  and  Shock  Resistance  with 
increasing  annealing  temperature  after  varying  amounts 
of  cold  work,  using  test  pieces  taken  from  sheets  10  mm. 
thick. 

Figs.  16  and  17,  corresponding  with  100  %  and  300  %  cold 
work  respectively,  summarise  the  results. 


THICK  SERIES 
(Test  Pieces  10mm.   thick) 


WOO  Kg 


100 


200          300          400 
Temperature 


500 


FIG.  16. — Variation  in  Mechanical  Properties  (Hardness  and 
Shock)  on  Annealing  after  100  %  Cold  Work. 

HARDNESS. 

The  hardness  curves  under  1000  kg.  and  500  kg.  are  shown 
in  the  figures.  These  curves  diverge  little  ;  they  are  practically 
identical  in  the  region  of  cold  work,  and  diverge  chiefly  in  the 
region  of  anneal,  where  the  hardness  under  1000  kg.  is  slightly 
greater  than  that  under  500  kg.  The  object  in  obtaining 


40 


ALUMINIUM  AND  ITS  ALLOYS 


these  curves  is  not  so  much  to  compare  the  actual  hardness 
numbers  under  500  and  1000  kg.,  as  to  gain  some  indication 
of  the  trend  of  these  values  under  two  different  loads.  The 
advantage  of  this  is  evident ;  for  instance,  in  the  case  of  higJi 
temperature  tests,  where  the  determination  of  hardness  under 


WOO  Kg 


THICK  SERIES 
(Test  Pieces  1 0mm.  thick) 


Shock 
Resistance 


Shock 
Resistance 
Kg.m 
Per 


200          300          400          500          600°C 

Temperature 

FIG.  17. — Variation  in  Mechanical  Properties  (Hardness  and 
Shock)  on  Annealing  after  300  %  Cold  Work. 

1000  kg.  would  not  be  possible,  the  hardness  must  be  determined 
under  500  kg.  Since  we  have  all  the  necessary  data,  we  may  then 
extend  our  results,  and  make  such  deductions  as  are  useful. 

It  is  evident  from  Figs.  16  and  17  that  the  hardness  curves 
exhibit  the  same  regions  as  the  curves  for  the  Tensile  properties, 
as  noted  above. 


MECHANICAL  PROPERTIES  41 

SHOCK  RESISTANCE. 

It  should  be  observed  that  in  the  cold- work  region  (0°-150°  c.) 
the  Shock  Resistance  remains  approximately  constant,  having 
a  value  of  about  4  kg.  m.  per  sq.  cm.  for  300  %  cold  work. 
It  rises  gradually  in  the  softening  region,  and  in  the  completely 
annealed  zone  it  reaches  8  kg.  m.  per  sq.  cm.  on  annealing  at 
400°  c.  after  100  and  300  %  cold  work.  It  continues  to  increase 
slowly  up  to  9  kg.m.  per  sq.  cm.  on  annealing  at  600°  after  100  % 
cold  work,  and  even  to  10  kg.  m.  per  sq.  cm.  on  annealing  at  this 
temperature  after  300  %  cold  work. 

C.    CUPPING  TESTS 
Depth  of  Impression  and  Breaking  Load 

EXPERIMENTAL  DETAILS. 

Cupping  tests  were  carried  out  on  sheet  metal  by  means  of 
the  Persoz  apparatus  (Fig.  18)  in  the  Chalais  laboratory. 

This  apparatus  consists,  essentially,  of  a  graduated  rod 
furnished  at  one  end  with  a  plate  and  at  the  other  with  a  ball 
20  mm.  in  diameter.  This  ball  rests  on  a  circle  90  mm.  in 
diameter  taken  from  the  sheet  to  be  tested  and  gripped  between 
two  serrated  annular  rings  of  50  mm.  internal  diameter. 

By  subjecting  the  whole  apparatus  to  a  compressional  stress 
between  the  two  plates  of  a  testing  machine,  steadily  increasing 
pressures  can  be  applied  to  the  centre  of  the  circle,  through  the 
ball.  This  compression  is  continued  right  up  to  the  point  of 
rupture  of  the  dome  which  forms,  in  the  sheet,  under  the 
pressure  of  the  ball. 

The  breaking  load,  and  the  depth  of  the  impression  made 
in  the  sheet,  at  the  point  of  rupture,  can  thus  be  measured. 
The  apparatus  permits  the  measurement  of  the  depth  of 
impression  with  a  maximum  error  of  -02  to  -03  mm. 

I.    Variation  of  Depth  of  Impression  and  Breaking  Load  with 
the  amount  of  Cold  Work. 

Figs.  19  and  20  summarise  the  results.  The  values  depend 
upon  two  variables  : — 

(i)  The  percentage  of  cold  work, 
(ii)  The  thickness  of  the  sheets. 

The  degrees  of  cold  work  investigated  were  0  %  (annealed), 
50  %,  100  %,  and  300  %,  and  the  sheets,  on  which  tests  were 


42 


ALUMINIUM  AND  ITS  ALLOYS 

I 


FIG.  18. — Persoz  Apparatus  for  Cupping  Tests. 


MECHANICAL  PROPERTIES 


43 


carried  out,  were  those  comprising  the  thin  series  ;    0-5  mm., 
1-0  mm.,  1-5  mm.,  and  2-0  mm.  in  thickness  respectively. 

Fig.  19  shows  for  each  thickness  the  variation  of  the  Depth 
of  Impression  and  Breaking  Load  with  cold  work. 

THIN  SERIES 


100  150          200 

Cold  Work 


250 


300% 


FIG.  19. — Cupping  Tests  :  Variation  in  Breaking  Load  and 
Depth  of  Impression  with  Cold  Work.  Test  pieces  of 
thickness  specified  (2-0,  1-5,  1-0,  and  0-5  mm.). 

It  shows  clearly  that  the  very  slight  increase  in  the  Breaking 
Load  due  to  the  cold  work  is  only  obtained  at  the  expense  of 
the  Depth  of  Impression  at  rupture. 

We  may  therefore  deduce  the  following  general  conclusion  : 


44 


ALUMINIUM  AND  ITS  ALLOYS 


The  absolute  minimum  cold  work  should  be  specified  for  sheet 
aluminium  required  for  pressing  or  other  work  of  a  similar 
nature.  The  amount  of  cupping,  which  annealed  sheet  will 
stand,  is  clearly  superior  to  that  which  sheet,  worked  even 
very  little,  can  support. 

THIN    SERIES 
1000  Kg. 

Breaking 
Load 


16 
15 

.  14 

13 


vt 

I 


o 

J= 

4-1 

Q. 

& 


900 


800 


700 


600 


500 


400 


100%  Cold 
50  %  Work 
0 


300  //, 


200 


100 


0-5  i-o  1-5 

Thickness  of  Sheet 


2-0  mm. 


FIG.  20. — Cupping  Tests  :  Variation  in  Breaking  Load  and  Depth  of 
Impression  with  thickness,  at  specified  amounts  of  Cold  Work 
(0,  50,  100  and  300  %). 

Fig.  20,  which  is  derived  from  Fig.  19,  shows  the  variation  of 
Breaking  Load  and  Depth  of  Impression  with  thickness  in  the 
case  of  test  pieces  having  been  subjected  to  0  %,  50  %,  100  %, 
and  300  %  cold  work  respectively. 

It  shows  that  an  increase  of  thickness  must  be  resorted  to, 
if  an  increased  cupping  value  is  desired. 

CONCLUSION.  Whatever  the  thickness,  all  sheet  destined  for 
pressing  should  be  annealed,  and  this  condition  should  be 
included  in  specifications. 

II.     Variation   of  Depth   of  Impression   and  Breaking  Load 
with  increasing  annealing  temperature,  after  varying  amounts 
of  Cold  Work. 
Investigations  were  made  on  test  pieces  of  the  thin  series  : 

Type  la  (0-5  mm.)  and  Type  Id  (2-0  mm.),  taken  from  sheet  cold 


MECHANICAL  PROPERTIES 


45 


worked  to  50  %,  100  %,  and  300  %.  Figs.  21,  22,  and  23 
summarise  the  results  obtained  on  Type  la  (0-5  mm.  thick). 
They  show  that  the  maximum  values  of  the  Depth  of  Impres- 
sion and  Breaking  Load  are  reached  in  the  region  375°-425°, 
and  these  values  remain  approximately  constant  up  to  600°. 


THIN  SERIES 
(Test  Pieces  O^mm.  thick) 


15 
14 
13 
12 
c  11 


10 


S.    8 

!   a 
Is 

Q 
4 

3 


Breaking 
Load 

Kg 
210 


200 


Uepth  of 
• 
Impression 


190 


180 


170 


160 


150 


Breaking 
Load 


100 


500 


600°C 


200          300          400 
Temperature 

FIG.  21. — Cupping  Tests  :  Variation  in  Breaking  Load  and  Depth 
of  Impression  on  Annealing  after  50  %  Cold  Work. 

They  show,  further,  that  the  final  results  (Depth  of  Impression 
and  Breaking  Load)  are  higher  as  the  initial  cold  work  is 
greater. 

The  following  table  summarises  the  results : — 


Initial  Cold  Work 
50% 
100  % 
300  % 


SHEETS  0-5  mm.  THICK 

After  Complete  Anneal 
Breaking  Load  Depth  of  Impression 

185kg.  llmm. 

195  kg.  12  mm. 

200kg.  12-5  mm. 


46 


ALUMINIUM  AND  ITS  ALLOYS 


Figs.  24,  25,  and  26  give  the  results  for  Type  Id  (2-0  mm. 
thick).  They  show  that  for  sheet  2-0  mm.  thick,  as  in  the 
case  of  sheet  0-5  mm.  thick,  the  Depth  of  Impression  and 
Breaking  Load  reach  their  maximum  values  in  approximately 
the  same  temperature  range,  but  slightly  extended  (375°-450°), 


THIN   SERIES 
(Test  Pieces  O'Smm.  thick) 


200  300          400 

Temperature 


600°C 


FIG.   22. — Cupping  Tests  :    Variation  in  Breaking  Load  and 
Depth  of  Impression  on  Annealing  after  100  %  Cold  Work. 

and  these  values  remain  approximately  constant  up  to  600°. 
The  same  remarks  as  before  apply  as  to  the  relation  between 
the  initial  cold  work  and  the  final  values  (Breaking  Load  and 
Depth  of  Impression  at  rupture).  The  following  table  may 
therefore  be  drawn  up  : — 

SHEETS  2-0  mm.  THICK 

After  Complete  Anneal 

Initial  Cold  Work  Breaking  Load  Depth  of  Impression 

50%  850kg.  16mm. 

100%  880kg.  16-2  mm. 

300%  950kg.  16-4  mm. 


MECHANICAL  PROPERTIES 


47 


D.    FINAL  SUMMARY 

In  this  chapter  the  following  properties  have  been  con- 
sidered : — 

(a)  Tensile  properties. 

(b)  Hardness  and  Shock  Resistance. 

(c)  Cupping  properties. 

THIN  SERIES 
Breaking    (Test  Pieces  0'5mm. thick) 


Depth  of 


15 

Breaking   x 

14 

Load 
Kg 

13 

12 

s11 

1  Impression  nf 

vj  00  <D  O  . 

200 

Impression 
Breaking 


100 


200  300          400 

Temperature 


500 


600'C 


FIG.  23. — Cupping  Tests  :    Variation  in  Breaking  Load  and 
Depth  of  Impression  on  Annealing  after  300  %  Cold  Work. 


The  work  has  been  carried  out  from  a  twofold  standpoint — 

(i)  Influence  of  cold  work, 
(ii)  Influence  of  annealing  after  cold  work, 

and  without  entering  into  minute  details,  already  given  under 
their  respective  headings,  we  may  draw  the  following  con- 
clusions : — 


48 


ALUMINIUM  AND  ITS  ALLOYS 


(i)  COLD  WORK. 

This  may  be  considered  under  two  headings  : — 

(a)  The  intermediate  cold-worked  state  during  manu- 
facture, whose  effect  is  removed  by  a  final  anneal. 

(6)  The  final  cold- worked  state  of  the  manufactured 
product. 

THIN  SERIES 
(Test  Pieces  2mm    thick) 

Depth  of 
Kg 


10 


•5    7 


6 

Q. 


1000 

Breaking 
Load 


950 


Impression 


900 


850 


800 


700 


100 


200     300     400 

Temperature 


500 


600  C 


FIG.   24.  —  Cupping  Tests  :    Variation  in  Breaking  Load  and 
Depth  of  Impression  on  Annealing  after  50  %  Cold  Work. 


(a)  Intermediate  Cold  Work. 

The  utilisation  of  large  amounts  of  cold  work,  200  and  300  %, 
possesses  certain  decided  advantages.  It  increases  generally 
the  value  of  the  mechanical  properties  obtained  after  a  com- 
plete anneal,  and  possesses  an  indubitable  economic  advantage 
in  dispensing  with  useless  intermediate  anneals. 


MECHANICAL  PROPERTIES 


49 


(b)  Final  Cold  Work. 

Cold  work  is  far  from  advisable,  particularly  in  aeronautical 
work.  It  hardly  seems  to  constitute  a  stable  state,  and  should 
especially  be  avoided  in  material  subjected  to  constant  vibration. 

We  are  therefore  of  the  opinion  that  aluminium  should  be 
used  in  the  annealed  condition,  certainly  as  regards  aero- 
nautical work  ;  the  increased  strength,  which  results  from 
cold  work,  as  described  in  this  chapter,  should  be  attained 
by  other  means,  such  as  increase  of  thickness,  or  the  employ- 
ment of  alloys. 

THIN  SERIES 
(Test  Pieces  2mm.  thick) 


15 


14 


13 


12 

E   n 
E 

c  10 
o 

1     9 
2 

a-    8 

~      7 
O 

-G     6 


Depth  of 
Impression 


900 


Breakim 
— 
Load 


850 


800 


750 


700 


100 


200     300     400 
Temperature 


500 


600°C 


FIG.  25. — Cupping  Tests  :   Variation  in  Depth  of  Impression 
and  Breaking  Load  on  Annealing  after  100  %  Cold  Work. 

(ii)  ANNEALING. 

We  have  pointed  out  the  existence  of  regions  of  cold  work, 
softening,  complete  anneal,  and  of  falling  off  of  ductility. 

Only  one  region,  that  of  complete  anneal,  produces  a  techni- 


50 


ALUMINIUM  AND  ITS  ALLOYS 


cally  finished  product.*  This  fixes  an  optimum  mean  annealing 
temperature  of  400°,  and  gives,  in  the  metal,  after  a  suitable 
initial  cold  work  (200  %-300  %),  the  following  properties  : — 

Elongation  %       =40 

Tensile  Strength  =11  kg.  per  sq.  mm.  (6-98  tons  per  sq.  in.). 

Elastic  Limit        =5         ,,         „          (3-17        ,,          „     ). 

Shock  Resistance=8-5  kg.  m.  per  sq.  cm. 

Brinell  Number    =23 


THIN  SERIES 
(Test  Pieces  2mm. 


16 


15 


14 


13 


^)  Depth  of 


12 


10 


|8 


Q. 
O 

Q 


Breaking 


Load 


900 


850 


800 


750 


700 


100 


500         600°C 


200  300  400 

Temperature 

FIG.  26. — Cupping  Tests  :  Variation  in  Depth  of  Impression 
and  Breaking  Load  on  Annealing  after  300  %  Cold  Work. 

*  An  intermediate  state,  producing  in  aluminium  a  Tensile  Strength 
higher  than  that  possessed  by  the  annealed  metal,  may  be  studied.  As  we 
have  seen,  this  cannot  be  achieved  by  a  slight  cold  working,  which  deprives 
the  metal  of  a  portion  of  its  Elongation,  but  only  by  submitting  it  to  an 
anneal  in  the  softening  region — an  incomplete  anneal.  But  the  improvement 
in  the  Tensile  Strength,  amounting  to  some  tons  per  sq.  in.,  is  only  realised 
at  the  expense  of  the  Elongation,  and  of  the  regularity  of  the  results.  The 
great  slope  of  the  curves  for  Tensile  Strength,  and  Elongation  %,  in  this 
softening  zone  shows  that  a  very  slight  variation  of  temperature  has  an 
enormous  influence  on  the  properties — hence  the  irregularity. 


MECHANICAL  PROPERTIES  51 

E.  CONTEMPORARY  LITERATURE  DEALING  WITH  THE  SUBJECT 
OF  THE  MECHANICAL  PROPERTIES  AFTER  COLD  WORK 
AND  ANNEALING. 

As  regards  the  variation  in  mechanical  properties  with  cold 
work  and  annealing,  aluminium  has  been  subjected  to  very 
detailed  investigation  by  Robert  Anderson,*  who  has  published 
the  following  articles  : — 

(1)  Erichsen    Tests    on    Sheet    Aluminium    ("  Iron    Age," 
llth  April,  1918,  pp.  950  and  951). 

(2)  Annealing   and   Recrystallisation   of   Cold-Rolled   Alu- 
minium Sheet   ("Metallurgical  and  Chemical  Engineering," 
Vol.  XVIII,  No.  10,  pp.  525-7,  15th  May,  1918). 

(3)  Tests  on  Sheet  Aluminium.     Softening  of  Cold-Rolled 
Sheet  by  heating  for  an  extremely  short  time  at  different 
temperatures.    Better  Properties  for  Drawing.    Effect  of  Over- 
annealing  ("  Iron  Age,"  18th  July,  1918). 

For  the  complete  report  we  must  refer  the  reader  to  the 
original  papers  dealing  with  these  most  interesting  investiga- 
tions, of  which  we  can  only  give  an  abridged  summary.  We 
may  say,  at  once,  that,  where  comparison  is  possible,  there  is  no 
contradiction  between  Anderson's  results  and  our  own,  as  given 
in  this  chapter.  Certain  experimental  methods  are  different. 

ANDERSON'S  DEFINITION  OF  MAXIMUM  SOFTENING  OR  ANNEAL. 

The  maximum  softening  is  defined  in  terms  of  the  Shore 
scleroscope  number.  The  metal  may  be  regarded  as  completely 
annealed  when  the  scleroscope  hardness  is  4-5,  this  being  the 
maximum  softness  from  the  point  of  view  of  practical  rolling. 
"  Sheets  having  this  degree  of  hardness,"  says  Anderson,  "  are 
as  soft  as  is  usual,  though  occasionally  cases  arise  where 
the  scleroscope  number  falls  to  3-5." 

ANDERSON'S  DEFINITION  OF  COLD  WORK. 

Anderson  defines  "  cold  work  "  or  "  percentage  reduction 
of  area  "  by  the  formula  : — 

Reduction  of  area  (o/o)=S(mitial)-S(final) 

S(imtial) 

This  gives,  for  the  same  deformation,  a  lower  percentage  than 
that  calculated  from  our  formula. 

*  Prior  to  the  work  of  Anderson,  a  paper  was  published  by  Carpenter  and 
Taverner,  "  The  effect  of  heat  at  various  temperatures  on  the  rate  of  softening 
of  cold-rolled  aluminium  sheet."  "  Journal  of  the  Institute  of  Metals,"  1917, 
and  "  Engineering,"  Vol.  CIV,  1917,  No.  8,  p.  312. 


52 


ALUMINIUM  AND  ITS  ALLOYS 


In  his  paper  on  "Annealing  and  Recrystallisation  of  Cold- 
Rolled  Aluminium  Sheet,"  the  author  proposes  particularly 
to  show  the  influence  of  the  duration  of  an  anneal  at  different 
temperatures  on  the  production  of  metal  suitable  for  drawing 
and  pressing  under  the  best  conditions. 

The  percentage  reduction  of  area  is  determined.  The  Shore 
scleroscope  number  shows  the  hardness  and  hence  the  degree 
of  softness.  The  Erichsen  machine*  shows  the  suitability  of 
the  metal  for  further  work,  not  only  by  the  depth  of  the  dome, 
but  by  the  large  or  small  appearance  of  the  grains.  The 
anneals  were  carried  out  in  a  laboratory  electric  furnace,  tem- 
peratures being  measured  to  the  nearest  5°C.,  and  the  times 
being  recorded. 

PAPER  OF  15TH  MAY,  1918  ("METALLURGICAL  AND  CHEMICAL 
ENGINEERING  ").  INFLUENCE  OF  TEMPERATURE  AND 
DURATION  OF  ANNEAL. 

Annealing  cold-rolled  aluminium  sheet  of  different  thick- 
nesses for  twenty -four  hours  at  370°  gave,  for  a  Shore  sclero- 
scope number  between  4  and  5,  Erichsen  domes  showing  gross 
crystallisation,  and  metal  little  suitable  .for  drawing. 

Systematic  tests  were  carried  out  on  sheet  of  thickness  and 
percentage  reduction  of  area  given  in  the  following  table  : — 


No. 

Thickness 
mm.                   inches 

%  Reduction 
of  Area 

Gaugef 

1 

2-58 

•1087 

54-85 

10 

2 

2-05 

•0841 

63-30 

12 

3 

1-70 

•0650 

71-60 

14 

4 

1-32 

•0512 

77-60 

16 

5 

1-09 

•0401 

82-60 

18 

6 

0-79 

•0321 

86 

20 

7 

0-68 

•0275 

88  rcj 

22 

8 

0-54 

•0220 

90-50 

24 

9 

0-40 

•0169 

92-70 

26 

10 

0-30 

•0128 

94-50 

28 

MINIMUM  TEMPERATURE  NECESSARY  FOR  OBTAINING  A  SCLERO- 
SCOPE NUMBER  OF  4-5. 

At  a  temperature  of  300°.  In  the  case  of  sheets  1  to  6  (inclusive), 
60  minutes  will  hardly  suffice  to  give  a  scleroscope  number 
of  4-5.  30  minutes  suffice  for  sheets  6  and  7,  and  20 
minutes  for  8,  9,  and  10. 

*  It  should  be  noted  that  in  the  Erichsen  machine,  only  the  Depth  of 
Impression,  and  not  the  corresponding  Breaking  Load,  is  measured, 
f  Brown  and  Sharp e  gauges. 


MECHANICAL  PROPERTIES 


53 


At  400°. 
At  600°. 


At  350°.     30  minutes  are  sufficient  for  sheet  1. 

20  minutes  are  sufficient  for  sheets  2  and  3. 
15  minutes  are  sufficient  for  sheets  4  to  10  (inclusive). 
10  minutes  are  sufficient  for  all  sheets. 
10  minutes  are  sufficient  for  reaching  a  scleroscope 
number  very  near  the  lower  limit. 

Anderson's  experiments,  in  agreement  with  ours,  show  that 
annealing  has  a  more  rapid  effect,  the  greater  the  initial  cold 
work.  They  further  show  that,  from  the  point  of  view  of 
working  and  of  fineness  of  grain,  it  is  necessary  to  investigate  the 
greatest  depth  of  impression  given  after  an  anneal  of  the 
shortest  possible  duration,  and  at  the  lowest  possible  tempera- 
ture, consistent  with  a  scleroscope  hardness  of  4-5  and  a 
smooth  Erichsen  dome.  Anderson  has  thus  established  the 
following  curve  (Fig.  27)  which,  for  the  conditions  just  stated, 


1   0 

Erichsen  _  0 
Number  !* 

1  1 

10 
(Depth   of 
lmpression)Q 

(mm.) 
8 

7 

tf^ 

i-~-— 

fi  

jy 

^' 

j* 

S* 

x 

./ 

/ 

\f 

/ 

J* 

f 

1 

0 


0-5 


VO 


1-5 


2-0 


•5  mm. 


Thickness 

FiG.    27. — Variation  in  Depth  of  Impression  with  Thickness. 
Annealed  Aluminium  Sheet. 

gives  the  curve  of  indentation  plotted  against  thickness  for 
annealed  aluminium  sheet.  Fig.  28  gives  the  curve  of  indenta- 
tion plotted  against  thickness  for  cold-rolled  aluminium  sheet. 

RECRYSTALLISATION. 

Anderson  has  carried  out  microscopic  examinations  of 
differently  worked  samples  annealed  for  30  minutes  at  350°. 

The  samples  having  percentage  reduction  of  area  of  54-85, 
63-30,  and  71-60  respectively  were  not  recrystallised.  Re- 
crystallisation  occurred  for  higher  percentages  of  deformation, 
which  shows,  again,  the  effect  of  cold  work  on  the  result  of 
an  anneal. 


54  ALUMINIUM  AND  ITS  ALLOYS 

Anderson's  work  shows  that  prolonged  annealing  is  very 
harmful,  and  also  that  not  only  must  the  temperature  be 
carefully  selected,  but  also  the  minimum  time  required  at  this 
temperature.  We  have  determined  this  minimum  time  by 
tests  preliminary  to  the  annealing  experiments.  The  times 
thus  determined  are  different  from  those  of  Anderson,  for  they 


1  1 

Erichsen  1  ° 
Number 
y 

8 
(Depth  of 
Impression)? 
(mm.) 
6 

5 

4 

3 

£") 

^^ 

***' 

^ 

s* 

r*^ 

^ 

' 

> 

& 

/ 

S 

/ 

f 

J 

¥ 

<f 

D            0-5          1-0          V5          2-0          2-5  mm. 
Thickness 

FIG.  28. — Variation  in  Depth  of  Impression  with  Thickness. 
Cold-Rolled  Aluminium  Sheet. 

refer  to  annealings  in  liquid  baths  (oil  or  salt),  for  which  the 
length  of  time  is  different  from  that  required  in  electric  or  gas 
furnaces. 

PAPER  OF  18TH  JULY,  1918  ("IRON  AGE"). 

Returning  to  the  question  in  this  paper,  Anderson  discusses 
the  harmful  effects  of  prolonged  annealing — "  over-annealing." 

He  points  out,  first  of  all,  the  inferior  results,  as  regards  the 
grain  size  of  the  metal,  of  annealing  aluminium  sheet,  1-70  mm. 
thick  (-0650  in.,  No.  14  gauge)  for  25  hours  at  370°,  and  shows 
the  good  results  obtained  by  annealing  metal  of  this  thickness 
for  2  hours  at  400°.  The  best  results  are  obtained  by  very 
short  anneals  (cf.  Fig.  29,  showing  the  effect  of  annealing  for 
different  lengths  of  time  at  430°) — considerations  which,  from 
the  industrial  and  commercial  standpoint,  are  of  value. 

Further,  two  types  of  anneal  may  be  distinguished  : — 

(i)  Intermediate, 
(ii)  Final. 


MECHANICAL  PROPERTIES 


55 


Intermediate  anneals  can  be  carried  out  in  the  neighbourhood 
of  the  upper  limit  of  the  region  of  complete  anneal,  450°  or  even 
500°,  employing  the  shortest  possible  time  consistent  with  the 
softening  of  the  metal.  The  employment  of  a  temperature 
higher  than  those  indicated,  necessitates  an  extremely  short 


Erichsen 
Number 

11 
(Depth 

of 

Impression 
mm.) 

10 


0   5   10  15  20  25  30  35  40  45  50  55  60  65 

Time  (minutes) 
FIG.  29. 

anneal ;  a  slight  variation,  therefore,  in  the  length  of  time, 
difficult  to  avoid  in  works  practice,  may  lead  to  large  irregu- 
larities. 

Final  anneals,  which  must  be  carried  out  very  precisely,  in 
order  to  obtain  regularity  in  the  finished  product,  are  conducted 
at  the  temperature  specified  above  (i.e.  375°-425°)  for  the 
minimum  length  of  time  possible,  which  is  easily  determined 
for  the  particular  temperature  employed. 


CHAPTER  IV 
MICROGRAPHY   OF   ALUMINIUM 

THE  micrography  of  pure  aluminium  presents  special  diffi- 
culties, not  generally  met  with  in  the  case  of  its  alloys.  The 
numerous  set-backs  experienced  in  this  method  of  examination 
have  hindered  its  standardisation. 

The  difficulties  lie  as  much  in  the  technique  of  polishing  as 
in  that  of  etching. 

POLISHING. 

The  difficulty  in  polishing  is  due  chiefly  to  the  softness  of 
the  metal,  which  tends  to  flow  or  to  become  hardened  under 
the  pressure  employed  ;  this  pressure  must,  therefore,  be  very 
slight — a  matter  of  practice  and  touch. 

The  particles  and  dust  of  the  emery  paper  become  embedded 
in  the  pores  of  the  metal.  R.  J.  Anderson  pointed  out  this 
difficulty  and  recommended  the  following  method  of  over- 
coming it,  based  upon  that  of  Gwyer  : — 

"  The  surface  is  levelled  off  with  a  fine  file,  followed  by 
dry,  coarse  emery  paper,  and  then  by  No.  0.  The  operation 
is  continued,  using  papers  No.  00,  000  and  0000,  covered  by 
a  thin  layer  of  paraffin  wax.  This  paraffin  film  prevents  the 
entrance  of  the  fine  emery  particles  into  the  metal,  and  gives 
a  very  satisfactory  polish.  Melted  paraffin  is  poured  on  the 
surface,  and  smothered  with  a  flat,  warmed  file.  The  papers 
are  secured  to  wooden  boards  or  to  a  polishing  disc.  The  last 
scratches,  caused  by  the  0000  paper,  are  removed  by  polishing 
on  cloth  with  fine  Tripoli  and  water.  The  darkening  of  the 
surface  caused  by  the  Tripoli  is  removed  by  polishing  on  a 
fine  cloth  with  a  non-alkaline  metal  polish." 

ETCHING. 

Both  potash  and  soda  (KOH,  NaOH)  have  been  used  as 
etching  reagent,  the  black  deposit  which  forms  being  removed 
by  immersion  in  a  dilute  solution  of  chromic  acid,  as  recom- 
mended by  Archbutt. 

The  best  results  have  been  obtained  using  hydrofluoric 

56 


PLATE   I. 


PHOTOGRAPH  1. 
ALUMINIUM  INGOT.     CHILL  CAST. 

><40. 
(Robert  J.   Anderson.) 


PHOTOGRAPH  2. 
ALUMINIUM  INGOT.     SAND  CAST. 

X50. 
(Robert  J.  Anderson.) 


:;V:v^.^?^'  --- 


^' 


PHOTOGRAPH  3. 

ALUMINIUM.     COLD  WORKED  (50  %). 
XlOO. 


PHOTOGRAPH  4. 

ALUMINIUM.     COLD  WORKED  (100  %): 
XlOO. 


To  face  page  57 


PLATE   II. 


PHOTOGRAPH  5. 
ALUMINIUM.     COLD  WORKED  (300  %). 

X60. 


PHOTOGRAPH  6. 
ALUMINIUM.      COLD  WORKED  (300  %) 

AND  SUBSEQUENTLY  ANNEALED  AT  350° 

FOR    10    MINUTES. 

XlOO. 


i  aw?./?® 
f  W£Mm 


PHOTOGRAPH  7. 
ALUMINIUM.     ANNEALED  AT  595°  FOR 

60    MINUTES. 

X50. 
(Eobert  J.  Anderson.) 


PHOTOGRAPH  8. 
ALUMINIUM.     ANNEALED  AT  595°  FOR 

4  HOURS. 

X50. 
(Robert  J.  Anderson.) 


To  face  page  57 


MICROGKAPHY  OF  ALUMINIUM  57 

acid  (HF),  as  suggested  by  Brislee,  employing  a  mixture  of  one 
part  of  fuming  hydrofluoric  acid  and  eight  parts  of  water. 
The  section  is  plunged  into  this  liquid,  and  the  blackening  of 
the  surface  is  removed  by  immersing  for  some  seconds  in  con- 
centrated nitric  acid.  Hydrogen  fluoride  vapour  may  equally 
well  be  employed  for  etching.  To  give  good  results,  the  hydro- 
fluoric acid  should  be  chemically  pure,  and  should  be  preserved 
and  used  in  vessels  coated  with  paraffin. 

RESULTS. 

Micrographs  of  aluminium  are  given  in  Plates  I  and  II. 
Photographs  1  and  2,  taken  from  the  work  of  R.  J.  Anderson, 
refer  to  chill  and  sand  castings. 

The  first  shows  the  dendritic  structure,  well  known  in  cast 
metals.  The  second  shows  crystals  of  aluminium  surrounded 
by  segregations. 

Photographs  3,  4,  and  5  refer  to  aluminium  cold  worked  to 
50,;  100,  and  300  %  respectively.  The  flow  lines  in  the  direction 
of  rolling  are  evident. 

Photographs  6,  7,  and  8  show  the  effect  of  annealing  after 
cold  work.  Photograph  6  shows  the  result  of  annealing, 
at  350°  for  10  minutes,  aluminium  previously  cold  worked 
to  300  %.  The  lines  of  flow  due  to  cold  work  have  not  dis- 
appeared, but  underneath  these  striations,  still  visible,  a  fine 
cellular  network,  characteristic  of  annealed  metal,  can  be  seen. 
The  striations  due  to  cold  work  only  disappear  on  heating 
either  for  a  longer  period  or  to  a  higher  temperature.  Photo- 
graphs 7  and  8  show  the  characteristics  of  a  metal  whose 
Elongation  has  diminished  as  a  result  of  over-annealing. 

The  thermal  and  mechanical  treatment  of  aluminium  can 
thus  be  controlled,  up  to  a  certain  limit,  by  micrographic 
examination,  as  can  also  the  purity  of  the  metal  and  the 
absence  of  dross. 


CHAPTER  V 
PRESERVATION   OF  ALUMINIUM 

WE  have  thought  it  best  to  consider,  in  a  special  chapter,  the 
subject  of  the  preservation  of  aluminium,  or,  if  it  be  preferred, 
of  its  changes  under  the  influence  of  physical,  chemical,  or 
mechanical  agencies. 

The  explanation  of  this  change  refers,  partly,  to  indisputable 
phenomena,  and  partly  to  hypotheses  which  probably  have 
the  advantage  of  lying  very  near  the  truth.  It  is  a  fact  that 
aluminium  changes  under  certain  conditions. 

Ditte,  H.  Le  Chatelier,  Ducru,  Heyn  and  Bauer  have  made 
investigations  and  published  papers  on  this  subject. 

EFFECT  OF  ATMOSPHERIC  AGENCIES 

The  effect  of  atmospheric  agencies  can  be  summarised  as 
follows  : — 

Am. 

Sheets  of  aluminium  were  protected  from  the  rain,  and 
exposed  to  the  atmosphere  by  Heyn  and  Bauer,  and  after  two 
hundred  days  had  not  changed  in  appearance. 

Ditte  explains  this  apparent  unchangeability  by  the  fact  that 
a  very  thin  film  of  alumina  is  formed,  which  protects  the  rest 
of  the  metal  from  all  change. 

WATER. 

Aluminium  is  attacked  by  distilled  water,  hydrated  alumina 
being  deposited.  According  to  Ditte,  this  thin  layer  of  alumina 
protects  the  aluminium  from  further  oxidation. 

AIR  AND  WATER. 

Air  and  ordinary  water,  acting  alternately,  have  less  effect 
than  water  alone. 

AIR  AND  SALT  WATER. 

The  views  of  Ditte  upon  this  subject  are  as  follows  : — 
"  Whenever  aluminium  is  in  contact  with  the  atmosphere, 

salt  water,  sea  water,  or  brackish  water,  the  metal  becomes 

58 


PRESERVATION  OF  ALUMINIUM  59 

coated  with  a  more  or  less  compact  layer  of  alumina,  possibly 
mixed  with  other  soluble  salts. 

After  the  aluminium  has  been  removed  from  the  liquid,  the 
change  will  continue  to  take  place,  if  the  metal  has  not  been 
entirely  freed  from  this  coating  and  has  not  been  sufficiently 
washed  so  as  to  remove  from  it  all  traces  of  alkali. 

Wherever  the  external  surface  of  the  metal  has  allowed  a 
trace  of  the  sea  salt  to  penetrate,  the  action  will  slowly  con- 
tinue, proceeding  the  more  rapidly  as  the  oxidised  substance 
is  more  hygroscopic,  and  permits  the  possible  chemical  re- 
actions to  take  place  more  easily." 

In  these  results,  the  molecular  state  of  the  metal  (anneal, 
degree  of  cold  work,  etc.)  has  not  been  taken  into  account. 
Then  the  following  questions  arise  : — 

Are  these  changes  solely  due  to  chemical  actions,  oxidations, 
tending  to  change  the  composition  of  the  metal  ? 

Are  they  due  to  disintegrations,  depending  upon  the  mole- 
cular state  of  the  aluminium  ? 

Are  they  due  to  the  ill-effects  of  cold  work,  giving  rise  to  a 
sort  of  spontaneous  anneal,  accompanied  by  disintegrations 
and  cracks  ? 

We  have  particularly  studied  this  phenomenon  in  the 
brasses,  whose  preservation  was  irretrievably  endangered,  if, 
after  cold  working,  a  certain  minimum  anneal  (350°)  had  not 
been  previously  carried  out. 

Cartridge  cases  and  artillery  shells  suffered  very  largely 
from  this  fault  before  the  remedy,  just  described,  was  applied. 

In  other  words,  is  the  disintegration  of  aluminium  connected 
with  chemical  causes  or  mechanical  causes  or  does  it  not 
depend  on  these  two  causes  together  ? 

The  following  literature,  referring  to  different  cases  of 
alteration,  will  enable  us  to  see,  up  to  a  certain  point,  what  are 
the  respective  parts  played  by  these  two  types  of  phenomena. 

Ducru*  observed  the  alterations  of  aluminium  for  the  first 
time  about  1894  in  the  case  of  wires  of  this  metal,  used  as 
telegraph  wires  in  the  Congo  or  Dahomey  from  the  coast  to 
the  interior.    In  a  month,  the  wire,  which  had  a  Tensile  Strength 
of  23  kg.  per  sq.  mm.  (14-6  tons  per  sq.  in.),  had  become  grey, 
and  changed  to  an  extremely    weak   substance.      Chemical    ^ 
analysis  showed  no  oxidation.    Hence  there  was  no  change  of     1 
a  chemical  nature.  4 

*  See  2nd  Report,  1911,  of  the  meeting  of  the  French  and  Belgian  members 
of  the  International  Association  for  testing  materials,  March  25th,  1911. 
Burdin,  Angers. 


60  ALUMINIUM  AND  ITS  ALLOYS 

The  same  phenomena  were  observed  in  the  case  of  a  sheet 
of  aluminium  at  Havre,  exposed  alternately  to  air  and  sea 
water  ;  in  this  instance,  at  the  end  of  three  months,  there  was 
superficial  oxidation. 

This  changed  layer  was  removed  by  planing  so  as  to  leave 
only  the  sound  portion.  Tests  on  this  showed  that  the  Tensile 
Strength  had  fallen  from  22  to  4  kg.  per  sq.  mm.  (14  to  2-54 
tons  per  sq.  in.).  At  all  events,  there  was  an  initial  cold  work 
clearly  indicated. 

In  1897,  Ducru  observed  the  alteration  of  aluminium  in 
utensils  made  by  pressing.  This  alteration  took  place  on  the 
bottom  of  the  utensil  in  the  following  manner  : — 

There  was  a  diminution  in  the  metallic  lustre  of  the  alu- 
minium, and  the  appearance  of  a  grey  colour,  becoming  more 
pronounced.  The  altered  portion  possessed  no  strength,  while 
analysis  showed  only  4  to  5  %  of  the  metal  to  be  changed  to 
alumina. 

Similar  observations  were  made  about  1911,  on  utensils, 
1  mm.  in  thickness,  made  by  pressing,  and  intended  for  domestic 
and  culinary  purposes.  The  same  changes  were  apparent,  and 
the  bottom  of  the  vessel  could  be  pierced  by  simple  pressure 
of  the  finger.  Analysis  showed  that  2-7  %,  3-7  %,  and  3-5  %, 
according  to  the  sample,  was  changed  to  alumina,  and  Ducru 
drew  the  following  conclusions  : — 

"  In  conclusion,  the  alteration  of  aluminium  appears,  at 
least  in  certain  cases,  to  have  one  peculiar  characteristic, 
namely,  that  it  is  not  an  oxidation  effect,  for  that  seems  to 
affect  only  a  small  portion  of  the  metal,  and  it  is,  on  the  other 
hand,  accompanied  by  a  diminution  in  mechanical  strength, 
which  causes  serious  trouble." 

Then,  if  the  phenomena  be  investigated  more  closely,  it  is 
evident  that  the  unfortunate  incidents  mentioned  have  occurred 
in  the  case  of  excessively  cold-worked  aluminium — wires, 
sheets,  or  pressed  utensils. 

The  external  agencies  play  the  part  of  accelerators,  assisting 
the  breakdown  of  equilibrium,  which,  in  their  absence,  would 
probably  only  have  been  delayed. 

We  have,  ourselves,  verified  these  disintegrations  due  to 
cold  work.  We  have  not  carried  out  experiments  on  alu- 
minium, but  the  investigations  we  have  made  on  the  cold 
working  of  brass  lead  us  to  infer  that  the  working  of  aluminium 
cannot  be  irrelevant  to  these  disintegrations. 

From  the  micrographic  standpoint,  worked  aluminium, 
similarly  to  worked  brass,  assumes  a  striated  appearance, 


PRESERVATION  OF  ALUMINIUM  61 

showing  crystalline  deformation  in  the  direction  of  the  mechani- 
cal work — a  condition  in  which  instability  is  probable. 

For  aeronautical  use,  where  security  is  essential,  the  need 
for  an  anneal  is  clearly  proved, — a  conclusion  supported  by 
the  arguments  already  given.  For  strengths  higher  than  that 
of  annealed  aluminium,  resource  must  be  had  to  its  alloys. 

For  purposes  in  which  safety  is  not  of  prime  consideration, 
and  in  which  the  high  strength  obtained  by  the  working  of 
aluminium  is  desirable,  the  problem  takes  on  another  aspect. 

The  practical  durability  of  cold-worked  aluminium  will  be 
a  predominant  factor  to  be  considered  in  solving  the  problem 
of  the  practical  and  economical  uses  of  which  it  is  capable 
(for  wires  and  cables  for  electrical  conductors). 


CHAPTER  VI 
SOLDERING   OF   ALUMINIUM 

AFTER  having  discussed  the  physical,  chemical,  and  mechanical 
properties,  we  may  say  a  few  words  about  the  soldering  of 
aluminium.  This  soldering  is  not  without  difficulties,  which 
are  both  of  a  physical  and  chemical  nature. 

(a)  PHYSICAL  DIFFICULTIES. 

Coefficient  of  Expansion.  Aluminium  possesses  a  high 
coefficient  of  expansion,  which  must  be  taken  into  considera- 
tion in  order  to  avoid  breakdowns.  As  its  tenacity  is  low  at 
high  temperatures,  there  is  a  possibility  of  rupture  occurring 
owing  to  the  relative  contraction  as  the  joint  cools  down. 

Melting  Point.  The  low  melting  point  of  aluminium,  650°, 
is  also  a  disadvantage.  If  the  temperature  of  the  blowpipe 
(generally  high)  is  not  very  carefully  regulated,  the  melting 
point  of  the  metal  may  be  reached  or  even  exceeded,  thus 
damaging  the  articles  to  be  soldered,  to  say  nothing  of  the 
deterioration  of  properties  resulting  from  overheating,  which 
cannot  be  remedied  by  subsequent  cold  work,  followed  by  an 
anneal  at  a  suitable  temperature  and  for  an  appropriate  time. 

(b)  CHEMICAL  DIFFICULTIES. 

These  difficulties  arise  from  the  impurities  of  the  metal 
and  of  the  soldering  alloys. 

Impurities.  The  impurities  have  been  divided  into  three 
groups  : — 

Group  I.  Iron-Silicon  Group.  Iron  and  silicon  have 
harmful  effects  in  aluminium  solders. 

It  is  impossible  to  eliminate  these  impurities  completely, 
but  their  amount  must  be  restricted  according  to  the  specifi- 
cations we  have  laid  down. 

The  alloys  of  iron  and  silicon  with  aluminium  are  very  weak 
and  constitute  the  weakest  parts  in  the  article.  The  over- 
heating, due  to  the  soldering,  facilitates,  therefore,  the  forma- 
tion of  a  very  weak  system,  consisting  of  the  alloys  of  these 

62 


SOLDERING  OF  ALUMINIUM  63 

impurities  with  the  aluminium,  which  is  liable  to  lead  to 
rupture.  Hence  a  metal  must  be  used  which  does  not  contain 
larger  amounts  of  impurities  than  the  maxima  previously 
specified. 

Group  II.  Minor  Impurities.  If  these  do  not  exceed 
the  maxima  stipulated,  they  do  not  cause  any  serious  incon- 
veniences. 

Group  III.  Alumina.  The  formation  of  alumina  is  un- 
avoidable during  soldering,  and  this  gives  rise  to  the  most 
serious  difficulties.  The  presence  of  alumina  between  the 
two  sheets  to  be  soldered  hinders  the  soldering,  if  means  are 
not  taken,  during  the  operation,  to  remove  it.  For  this  pur- 
pose, a  flux  is  used,  which  must  fulfil  certain  prescribed  technical 
conditions. 

The  following  flux  is  recommended  by  "  L'Union  de  la 
Soudure  Autogene  "  : — 

Lithium  chloride .  .  ;.;  15% 

Potassium  chloride  .  .  .  45  % 

Sodium  chloride  .  r.  .  30% 

Potassium  fluoride  .  ,  7% 

Sodium  bisulphate  .  ,  3  % 

The  bisulphate  of  soda,  under  the  action  of  heat,  reacts 
with  the  chlorides  and  fluorides  forming  hydrochloric  and 
hydrofluoric  acids,  which  attack  the  alumina,  producing  the 
volatile  chloride  and  fluoride  of  aluminium. 

SOLDERING  ALLOYS. 

Generally,  the  alloys  for  soldering  aluminium  are  not  satis- 
factory. In  order  to  effect  soldering,  i.e.  for  alloying  to  take 
place,  the  temperature  must  be  relatively  high  and  then  the 
disadvantages  pointed  out  as  a  result  of  overheating  are  to 
be  feared. 

Galvanic  couples,  in  presence  of  salt  solutions,  may  lead  to 
disintegrations  of  the  metal. 

To  sum  up,  we  are  forced  to  the  following  conclusions 
concerning  the  soldering  of  aluminium  : — 

(1)  The  metal  used  must  be  as  pure  as  possible. 

(2)  A  flux  must  be  employed  to  remove  the  alumina,  which 

hinders  soldering. 

(3)  Preferably,  autogenous  welding  should  be  used. 


BOOK  II 
'^/ALLOYS    OF   ALUMINIUM 


CLASSIFICATION  OF  ALLOYS 

As  regards  abridged  notation  and  nomenclature  of  alloys, 
we  shall  conform  to  the  methods  prescribed  by  the  Permanent 
Commission  of  Standardisation  in  Paper  A2,  July  28th,  1919, 
on  "  The  Unification  of  Nomenclature  of  Metallurgical 
Products." 
Thus,  for  example,  the  abridged  notation  of  an  alloy  may  be 

Al        Gun        Sn,        Nil 

showing  that  we  are  dealing  with  an  alloy  of  aluminium 
containing  n  %  copper 

3  %  tin. 
1  %  nickel. 

According  to  the  classification  adopted  (see  page  xi),  we 
have  to  consider 

(1)  Light  alloys  of  aluminium  for  casting  purposes. 

(2)  Light  alloys  of  aluminium  of  great  strength  (Tensile 

Strength  greater  than  35  kg.  per  sq.  mm.  (22-22  tons 
per  sq.  in.)). 

A  typical  light  alloy  of  these  two  classes  has  a  density  less 
than  3-5,  and  in  the  majority  of  light  alloys,  as  we  shall  see, 
the  density  is  less  than  3. 

(3)  Heavy  alloys   of   which   aluminium  is    a   constituent, 

comprising  especially  the  "cupro-aluminiums,"  that 
is  to  say,  alloys  of  copper  and  aluminium  containing 
1-20  %  of  aluminium  with  less  than  1  %  of  other  im- 
purities. 

Copper  being  the  principal  constituent,  an  alloy  of  copper  con- 
taining 10  %  of  aluminium,  for  example,  would  be  represented 
by  the  symbol  CuAl10  and  the  special  cupro-aluminium  alloy  con- 
taining 9  %  of  aluminium  and  1  %  of  manganese  by  CuAlsMnj. 

These  alloys  are  often  known  as  aluminium  bronzes,  though 
the  name  aluminium  bronze  should  be  restricted  to  alloys  of 
copper  and  tin  containing  aluminium,  such  as  the  aluminium 
bronze  for  bearings  whose  symbolic  notation  is  CuSn44Al3. 

67 


68  ALUMINIUM  AND  ITS  ALLOYS 

Moreover,  in  the  nomenclature  of  alloys,  we  shall  invariably 
put  first  the  principal  metal,  followed  by  the  other  metals 
which  are  present  as  added  constituents.  Thus  the  name — 
"  aluminium-zinc  alloys  " — refers  to  those  rich  in  aluminium 
and  which  therefore  come  under  the  heading  of  light  alloys, 
while  the  name  "  zinc-aluminium  alloys  "  refers  to  those  rich 
in  zinc,  which  are  not,  therefore,  classed  as  light  alloys,  but 
as  heavy  alloys.  These  heavy  alloys  are  only  of  value  in 
aeronautical  construction  if  some  special  properties  compensate 
for  their  weight. 

After  dealing  with  the  alloys  of  the  three  groups  of  which 
we  have  made  a  special  investigation,  we  shall  summarise 
shortly,  in  a  special  section,  the  properties  of  the  principal 
alloys  in  the  group  which  have  been  studied  by  previous 
investigators.  Before  discussing,  in  the  following  chapters, 
the  investigations  on  these  alloys,  we  think  it  advisable  to 
recall  the  important  part  played  by  copper  in  the  alloys  of 
aluminium.  Since  the  majority  of  the  alloys  of  these  three 
groups  are  affected  by  this  constituent,  it  seems  suitable  to 
consider  it  separately,  before  entering  into  a  detailed  study 
of  each. 

EQUILIBRIUM  DIAGRAM  OF  COPPER- ALUMINIUM  ALLOYS. 

The  diagram  was  first  established  by  H.  Le  Chatelier,  then 
by  Campbell  and  Mathews,  Carpenter  and  Edwards,  Gwyer, 
and  Curry.  There  are  few  differences  between  these  various 
diagrams. 

We  give  Curry's  diagram  (Fig.  30),  and  the  results  of  the 
micrographic  examination  may  be  summarised  as  follows  : — 

Three  regions  may  be  distinguished : — 

First  Region.  Alloys  rich  in  copper  (100  %-86  %  by  weight 
of  copper). 

In  the  region  extending  from  100  %-92  %  of  copper,  the 
alloy  consists  of  a  solid  solution,  known  as  a,  while  from  92  %- 
86  %  of  copper  the  solid  solutions  a  and  y  are  present. 

The  latter  region  can  be  further  divided  into  two,  namely : — 

( solution  a 
92  %-88  %  copper  + 

leutectic  (a+y) 

/  solution  y 
88  %-86  %  copper  + 

\  eutectic  (a+y) 


CLASSIFICATION    OF  ALLOYS 


69 


At  88  %  of  copper,  therefore,  the  alloy  consists  of  the  eutectic 
(a+y),  formerly  called  jS.  This  use  of  the  name  j8  is  incorrect, 
since  the  constituent  j3  corresponds  with  austenite  in  steels — 
we  shall  not  employ  it.  The  solution  a  would  correspond,  in 
steels,  with  a  iron,  the  solution  y  with  cementite,  and  the 
eutectic  (a +y)  with  pearlite. 


noo 


1000 


900 


800 


700 


600 


500 


100      90       80        70       60       50       40       30       20        10 


100%Cu          90  80  70        60      50    40  30  20  10  0%(by  weight) 

Fio.  30. — Copper- Aluminium  Diagram  (after  Curry). 

The  heavy  alloys  of  great  strength,  that  is,  the  cupro-alu- 
miniums,  or  aluminium  bronzes,  are  contained,  approximately, 
in  the  region  from  92  %  to  88  %  of  copper,  i.e.  the  region  corre- 
sponding with  the  solution  a  and  the  (a-fy)  eutectic. 

Second  Region.  This  is  a  middle  zone,  extending  from  86  % 
to  54  %  of  copper,  in  which  a  certain  number  of  constituents 
exist  which  have  been  differently  named  by  the  various  in- 
vestigators. The  corresponding  alloys  are  weak  and  of  no 
industrial  importance. 


70  ALUMINIUM  AND  ITS  ALLOYS 

Third  Region.  This  extends  from  54  %  to  0  %  of  copper. 
The  alloys  consist  of  the  constituents  CuAl2  and  77,  the  latter 
being  a  solid  solution  of  copper  in  aluminium  containing  a  very 
low  percentage  of  copper. 

This  region  may  be  divided  into  two  :  — 

(a)  Between  54  %  and  30  %  of  copper,  in  which  the  con- 
stituents CuAl2  and  eutectic  occur,  the  eutectic  being 


(b)  Between  30  %  and  0  %  of  copper,  in  which  the  con- 
stituent 77  and  the  eutectic  just  mentioned  occur. 

It  must  be  noted  that,  for  low  amounts  of  copper,  the 
constituent  77  is  present  alone,  without  any  eutectic.  At 
30  %  of  copper  the  alloy  would  consist  only  of  the  (CuAl2-f  77) 
eutectic. 

The  only  part  of  this  region  which  is  of  industrial  importance 
is  that  extending  from  12  %  to  0  %  of  copper,  which  corresponds 
with  the  light  alloys  of  low  strength  for  casting  purposes. 

Hence  we  shall  only  deal  with  the  two  extremities  of  the 
equilibrium  diagram  of  the  copper-aluminium  alloys. 


PART  III 

LIGHT  ALLOYS  OF  ALUMINIUM  FOR 
CASTING  PURPOSES 

WE  have  no  intention  of  considering  the  details  of  the  casting 
of  aluminium,  and  have  no  wish  to  discuss  all  the  possible 
alloys  of  aluminium  used,  or  usable  for  this  purpose.  We  shall 
simply  give  the  results  of  experiments  carried  out  on  a  certain 
number  of  these,  particularly  those  which  have  been  used  in 
aeronautical  work.  We  shall  conclude  this  account  with  a 
summary  of  the  properties  of  certain  other  alloys,  as  investi- 
gated and  tested  in  France  and  other  countries. 

First  of  all  we  shall  summarise  the  different  legitimate 
requirements  as  regards  the  quality  of  aluminium  and  its  alloys 
used  for  casting. 

PROPERTIES  OF  ALUMINIUM  CASTING  ALLOYS. 

The  following  are  the  most  important,  especially  from  the 
aeronautical  standpoint. 

(1)  Lightness. 

(2)  Minimum  of  blowholes  and  porosity. 

(3)  A  sufficiently  great  Tensile  Strength,  Elastic  Limit,  and 

Hardness. 

And,  for  articles  used  at  high  temperatures,  such  as  pistons, 
motor  cylinders,  etc. : — 

(4)  A  certain  minimum  hardness  throughout  the  range  of 

temperature  experienced. 

(5)  Maximum  thermal  conductivity  and  specific  heat.    We 

may  say  at  once  that  pure  aluminium  will  not  satisfy 
all  these  requirements,  and  that  it  is  even  difficult  to 
find  an  alloy  that  will  completely  fulfil  all  these  con- 
ditions, which  we  shall  discuss  in  turn. 

(1)  Lightness. 

The  pure  metal  best  satisfies  this  condition,  the  alloys  rich 
in  magnesium  alone  being  superior  in  this  respect. 

71 


72  ALUMINIUM  AND  ITS  ALLOYS 

The  addition  of  other  constituents,  however,  ought  not  to 
deprive  the  alloy  of  the  lightness  due  to  the  aluminium. 

One  of  the  great  advantages  of  the  low  density  consists  in 
the  removal  of  the  critical  period  of  vibration*  outside  the 
regular  period  of  the  moving  system.  A  critical  period  of 
vibration  obtains,  when  there  is  coincidence  between  the 
frequency  of  the  particular  part  in  question  and  the  displace- 
ment frequency  of  the  system  of  which  it  forms  a  part — a 
persistence  of  these  conditions  may  lead  to  rupture. 

If  aluminium  be  substituted  for  steel,  and  the  area  of  cross 
section  be  doubled,  there  is  still  a  reduction  in  weight  and  a 
vibration  frequency  four  times  greater  which  displaces  the 
critical  resonance  range  a  certain  number  of  octaves,  thus 
making  harmful  coincidences  more  improbable. 

A  maximum  density  of  3  should  be  specified. 

(2)  Minimum  of  Blowholes  and  Porosity. 

The  cast  article  must  be  sound,  having  as  few  blowholes  as 
possible. 

A  high  percentage  of  alumina  seems  to  cause  blowholes  in 
the  cast  aluminium  article,  and  hence  renders  it  useless. 

Porosity  must  be  avoided.  In  the  pistons  of  aeroplane 
engines,  porosity  invariably  leads  to  erosion,  on  account  of 
the  hot  gases  being  continually  forced  through  the  article. 
Porosity  also  prevents  watertightness.  It  is  detected  by  special 
tests  and  is  usually  avoided  by  the  skill  of  the  founder. 

(3)  A   sufficiently  great   Tensile  Strength,  Elastic  Limit,  and 

Hardness. 

Pure  cast  aluminium  has,  in  the  cold,  the  following 
properties  : — 

Tensile  Strength  (average )j=  7  kg.  per  sq.  mm.  (445  tons  per 

sq.  in.). 

Elastic  Limit  „       =3-5  kg.  per  sq.  mm.  (2-22  tons  per 

sq.  in.). 

%  Elongation  =  7 

Shock  Resistance  =  2  kg.  m.  per  sq.  cm. 

Brinell  Hardness  =  23 

and  is  unsuitable  for  most  articles. 

It  is  obvious  that  a  Tensile  Strength  comparable  with  that 
obtained  after  forging  or  rolling  cannot  be  expected  in  a  cast 
alloy. 

*  Cf.  Fleury  and  Labruy^re,  "  Des  emplois  de  1' Aluminium  dans  la  con- 
struction des  Machines  "  (Dunod  and  Pinat,  1919). 


LIGHT  ALLOYS  OF  ALUMINIUM 


73 


From  this  point  of  view  the  requirements  must  be  modest, 
varying  between  8  and  20  kg.  per  sq.  mm.  (5-08  and  12-7  tons 
per  sq.  in.),  according  to  the  added  constituents  and  the 
method  of  casting  (chill  or  sand). 

The  Elastic  Limit  is  generally  very  near  the  Tensile  Strength, 
and  is  sometimes  indistinguishable  from  it. 

The  Elongation  is  always  very  low,  and  the  Hardness  varies 
as  does  the  Tensile  Strength. 

Very  little  must  be  expected  as  regards  Shock  Resistance 
also,  no  cast  alloy  having,  to  our  knowledge,  an  appreciable 
shock  resistance  ;  they  are  all  more  or  less  brittle. 

It  is  essential  to  take  this  fact  into  consideration  in  speci- 
fying the  method  of  working  for  cast  articles. 

For  articles  subjected  to  high  temperatures,  which  is  the 
case  in  the  majority  of  parts  of  machines,  the  following  proper- 
ties are  required : — 

(4)  A  certain  Minimum  Hardness  up  to  the  Maximum  Tempera- 
ture  reached. 

Pure  aluminium  does  not  possess  sufficient  hardness  as  the 
temperature  rises.  Parts  of  engines,  such  as  cylinders  and 
pistons,  may  reach  a  temperature  of  200°-300°. 

100 

90 

80 

£    70 

5 

E    60 

3 

Z  50 
1  40 
(D  30 

20 

10 


100 


500 


600  °C 


200          300          400 

Temperature 

FIG.  306. — Hardness  of  Aluminium  at  High  Temperatures 
under  500  Kg.  load. 

In  order  to  avoid  collapse,  those  parts  subjected  to  stress 
should  possess,  throughout  the  whole  range  of  temperature 
experienced  during  working,  certain  minimum  properties. 


74  ALUMINIUM  AND  ITS  ALLOYS 

As  regards  hardness,  this  can  be  expressed  approximately  by 
a  Brinell  number  of  about  30  under  a  load  of  500  kg. 

This  number  is  greater  than  that  of  aluminium  in  the  cold, 
and  necessitates  an  original  hardness  of  50  to  60. 

Tests  have  been  carried  out  on  a  certain  number  of  alloys 
in  order  to  examine  these  properties  at  high  temperatures. 

Fig.  30&  shows  the  hardness  of  aluminium  at  different 
temperatures,  and  enables  us  to  see  how  the  hardness  is  in- 
creased by  the  addition  of  various  constituents. 

(5)  A  Maximum  Thermal  Conductivity  and  Specific  Heat. 

A  high  conductivity  prevents  local  heating,  which  rapidly 
causes  deterioration,  and  renders  the  article  useless. 

Alloys  of  aluminium  possess  great  advantages  in  this  respect. 
We  know  that  the  conductivity  of  aluminium  is  36,  that  of 
silver  being  100  and  of  copper  75-11 — it  is  third  as  regards 
thermal  conductivity.  This  fact  is  of  very  great  importance  ; 
it  renders  the  employment  of  aluminium  alloys  for  pistons  very 
successful. 

On  the  other  hand,  the  specific  heat  of  aluminium  is  very 
high,  which  reduces  the  rise  in  temperature.  This  property, 
added  to  the  high  thermal  conductivity,  causes  aluminium 
pistons  to  become  far  less  heated  in  use  than  pistons  of  cast 
iron. 

The  temperature  reached  is  lower  than  that  of  decomposition 
of  the  lubricating  oils,  so  that  carbonaceous  deposits,  similar  to 
those  produced  on  cast-iron  pistons,  are  not  formed  on  pistons 
of  alloys  of  aluminium — for  this  reason  fouling  and  seizing 
do  not  occur. 

After  this  short  discussion  we  will  consider  individually  the 
alloys  which  we  have  investigated  or  met  with  in  practice. 

ALLOYS  OF  ALUMINIUM  FOR  CASTING  PURPOSES. 
The  following  alloys  have  been  considered : — 

(a)  Binary  aluminium-copper  alloys — the  study  of  the  part 

of  the  equilibrium  diagram  of  the  aluminium-copper 
alloys  extending  from  100  %  to  88  %  of  aluminium. 

(b)  Ternary  alloys — aluminium-copper-zinc. 

(c)  Quaternary  alloys — aluminium-copper-tin-nickel. 

We  conclude  the  account  of  the  tests  carried  out  on  these 
alloys  by  referring,  in  a  special  section,  to  certain  other  alloys 
belonging  to  the  group,  namely  : — 


LIGHT  ALLOYS  OF  ALUMINIUM  75 

Alloys  of  aluminium  and  tin. 
Alloys  of  aluminium  and  zinc. 
Alloys  of  aluminium  and  magnesium. 

As  far  as  possible,  we  shall  compare  the  properties  of  the 
cast  alloys  with  those  of  the  same  alloys  when  forged  or 
rolled. 

These  alloys  have  been  worked  in  the  following  manner  : — 

(1)  Casts. 

Some  heats  were  cast  directly  into  chills  without  runners. 
Ten  casts  were  made  for  each  alloy  in  cylinders  50  mm.  hi 
diameter  and  50  mm.  in  length. 

In  five  casts  two  tensile  and  two  shock  test  pieces  were 
made  per  cast,  the  operation  being  carried  out  in  such  a  way 
as  to  obtain  a  tensile  test  piece  at  one  end  and  a  shock  test 
piece  at  the  other  end  of  the  heat,  and  one  tensile  and  one 
shock  test  piece  towards  the  middle  of  the  heat. 

In  the  other  casts,  cylindrical  bars  were  made  for  hardness 
tests  at  high  temperatures.  These  were  carried  out,  using 
a  10  mm.  ball  and  loads  of  500  and  1000  kg. 

(2)  Test  Pieces. 

These  were  cast,  on  the  one  hand  in  chills,  and  on  the  other 
hand  by  bottom  pouring,  the  test  pieces  being  fed  by  lateral 
runners. 

These  two  types  of  tests,  the  one  on  sand  cast,  and  the  other 
on  chill  cast  test  pieces,  seemed  indispensable  in  order  to  show 
the  different  results  obtained  by  the  two  methods. 

In  general,  casting  is  carried  out  by  the  latter  method, 
while  the  real  and  intrinsic  properties  of  the  alloy  are  revealed 
by  the  former. 

We  should  render  ourselves  liable  to  error,  if  we  took,  as 
the  figure  for  Tensile  Strength,  that  determined  on  the  sand 
cast  samples. 

Tests  on  the  sand  cast  test  pieces  indicate  the  success  or 
failure  of  the  alloy,  but  do  not  show  the  true  properties 
possessed  by  the  chill  cast  article. 

(a)  BINARY  ALLOYS — ALUMINIUM-COPPER. 
The  following  types  are  considered  :— 

Type     I    .          ...       4  %  copper. 
„      II   y      •  ;       v      8%       „ 

,,  in  .      ,      *  12  %    „ 


76  ALUMINIUM  AND  ITS  ALLOYS 

TYPE  I  (4  %  COPPER) 
Analysis 

Aluminium,  alumina         .         .         .  94-25 

Copper 4-70 

Iron       .          .          .          .          .          .  0-57 

Silicon 0-48 

Density:    2-75 

Mechanical  Properties  (as  cast). 

The  average  mechanical  properties  may  be  summarised  as 
follows  : — 

(a)  Tests  on  Sand  Castings. 

Tensile  Strength  =  11  kg.  per  sq.  mm.  (6-98  tons  per  sq.  in.). 

%  Elongation      =3 

Shock  Resistance =0-6  kg.  m.  per  sq.  cm. 

(b)  Tests  on  Chill  Cast  Bars. 

Tensile  Strength=  13-7  kg.  per  sq.  mm.  (8-70  tons  per  sq.  in.) 
%  Elongation    =3-8 

The  Elastic  Limit  is  approximately  the  same  as  the  Tensile 
Strength. 

In  the  forged  or  rolled  state,  this  same  alloy  may  giye  : — 

Tensile  Strength =20  kg.  per  sq.  mm.  (12-7  tons  per  sq.  in.) 
Elastic  Limit      =  8  kg.  per  sq.  mm.  (5-08  tons  per  sq.  in.) 
%  Elongation    =10 

Hardness  at  High  Temperatures. 

The  results  of  the  hardness  tests  at  high  temperatures  are 
shown  in  Fig.  31. 

TYPE  II  (8  %  COPPER) 
Analysis 

Aluminium,  alumina         .          .          .90-07 

Copper 8-65 

Iron 0-84 

Silicon 0-44 

Density:  2-92 

Mechanical  Properties  (as  cast). 

The  average  mechanical  properties  may  be  summarised  as 
follows : — 


LIGHT  ALLOYS  OF  ALUMINIUM 


77 


O    50    TOO   150   200   250   300   350   400°C 

Temperature 

FIG.  31. — Hardness  of  Copper- Aluminium  Alloy,  containing  4  % 
Copper,  at  High  Temperatures  under  500  and  1000  Kg.  load. 


50        100      150      200      250      300 
Temperature 

FIG.  32.— Hardness  of  Copper-Aluminium  Alloy,  containing  8  % 
Copper,  at  High  Temperatures  under  500  and  1000  Kg.  load. 


78  ALUMINIUM  AND  ITS  ALLOYS 

(a)  Tests  on  Sand  Castings. 

Tensile  Strength    =  1 1  kg.  per  sq.  mm.  (6-98  tons  per  sq.  in.) 

%  Elongation        =0-7 

Shock  Resistance  =0-3  kg.  m.  per  sq.  cm. 

(b)  Tests  on  Chill  Cast  Bars. 

Tensile  Strength    =12-3  kg.  per  sq.  mm.  (7-81  tons  per  sq.  in.) 
%  Elongation        =0-7 

The  Elastic  Limit  is  approximately  the  same  as  the  Tensile 
Strength. 

The  results  of  the  hardness^  tests  at  high  temperatures  are 
summarised  in  Fig.  32. 

TYPE  III  (12  %  COPPER) 
Analysis 

Aluminium,  alumina         .          .          .  86-24 

Copper 12-65 

Iron 0-88 

Silicon 0-43 

Density:  2-95. 

Mechanical  Properties  (as  cast). 

The  average  mechanical  properties  may  be  summarised  as 
follows  : — 

(a)  Tests  on  Sand  Castings. 

Tensile  Strength    =  13  kg.  per  sq.  mm.  (8-25  tons  per  sq.  in.) 

%  Elongation       =0-8 

Shock  Resistance  =0-2  kg.  m.  per  sq.  cm. 

(b)  Tests  on  Chill  Cast  Bars. 

Tensile  Strength    =  13-6  kg.  per  sq.  mm.  (8-64  tons  per  sq.  in.) 
%  Elongation       =1 

The  Elastic  Limit  is  approximately  the  same  as  the  Tensile 
Strength. 

The  results  of  the  hardness  tests  at  high  temperatures  are 
summarised  in  Fig.  33. 

The  variations  in  the  hardness  at  high  temperatures  with  the 
copper  content  are  shown  in  Fig.  34. 

Allowing,  with  a  view  to  avoiding  the  possibility  of  collapse, 
a  minimum  Brinell  hardness  of  30,  it  is  evident  that  the  alloy 


LIGHT  ALLOYS  OF  ALUMINIUM 


79 


150 
140 
130 
120 
110 

1 100 

1  30 

z 


300   350   400°C 


50        100       150      200      250 

Temperature 

FIG.  33. — Hardness  of  Copper-Aluminium  Alloy,  containing  12  % 
Copper,  at  High  Temperatures  under  500  and  1000  Kg.  load. 


WO«C 


FIG.  34. — Variation  in  Hardness  under  500  Kg.  load,  with  Copper 
content  at  Temperatures  0°,  100°,  200°,  300°,  350°,  and  400°  C. 


80  ALUMINIUM  AND  ITS  ALLOYS 

containing  4  %  copper  can  be  used  for  the  range  of  temperature 

0-275°, 

the  alloy  having  8  %  copper  over  the  range  0-310°, 
and  the  alloy  having  12  %  copper  over  the  range  0-320°. 

It  must  be  noted  that  cold  working  cannot  be  employed  to 
increase  the  hardness,  since  its  effect  must  be  nullified  by  the 
rise  in  temperature. 

(b)  TERNARY    ALLOYS — ALUMINIUM-COPPER-ZINC    (12-13  % 
ZINC,  3  %  COPPER). 

Analysis 

Aluminium,  alumina         .          .          .  83-75 

Copper 3-10 

Zinc 11-60 

Lead 0-22 

Iron 0-88 

Silicon 0-55 

Density:  2-94. 

Mechanical  Properties  (as  cast). 

The  average  mechanical  properties  may  be  summarised  as 
follows : — 

(a)  Tests  on  Sand  Castings. 

Tensile  Strength    =  11  kg.  per  sq.  mm. (6-98  tons  per  sq.  in.) 

%  Elongation       =0-3 

Shock  Resistance  =0-6  kg.  m.  per  sq.  cm. 

(b)  Tests  on  Chill  Cast  Bars. 

Tensile  Strength  =16-5  kg.  per  sq.  mm.  (10-48  tons  per  sq.  in.) 
%  Elongation      =2-8 

For  the  same  copper  content,  the  Elastic  Limit  is  approxi- 
mately the  same  as  the  Tensile  Strength.  If  the  amount  of 
zinc  be  increased  to  13  %,  the  values  become  : — 

Tensile  Strength    =18-4  kg.per  sq.mm.(l  1  -68  tons  per  sq.  in.) 
%  Elongation        =4 

The  results  of  the  hardness  tests  at  high  temperatures  are 
summarised  in  Fig.  35,  which  shows  the  rapid  falling  off  in 
hardness  as  the  temperature  is  increased.  The  hardness  at 
ordinary  temperatures,  however,  is  greater  than  that  of  the 
majority  of  other  casting  alloys. 


LIGHT  ALLOYS  OF  ALUMINIUM 


81 


(c)   QUATERNARY  ALLOYS — 

Analysis 

Aluminium,  alumina 
Copper  .... 
Tin         .... 

Nickel    .... 

Iron 

Silicon  V"       « 

Density:  2-98 


84-93 
10-14 
3-20 
0-86 
0-48 
0-27 


50        100 


300      350      400°C 


150      200      250 

Temperature 

FIG.  35. — Hardness  of  Zinc -Copper- Aluminium  Alloy,  con- 
taining 12  %  Zinc,  3  %  Copper,  at  High  Temperatures 
under  500  and  1000  Kg.  load. 

Mechanical  Properties  (as  cast). 

The  average  mechanical  properties  may  be  summarised  as 
follows : — 

(a)  Tests  on  Sand  Castings. 

Tensile  Strength    =  13  kg.  per  sq.  mm.(8-25  tons  per  sq.  in.) 

%  Elongation       =1 

Shock  Resistance  =0-3  kg.  m.  per  sq.  cm. 

(b)  Tests  on  Chill  Cast  Bars. 

Tensile  Strength    =12-6  kg.  per  sq.mm.(8-00  tons  per  sq.  in.) 
%  Elongation       =0-5 


82 


ALUMINIUM  AND  ITS  ALLOYS 


The  Elastic  Limit  is  approximately  the  same  as  the  Tensile 
Strength. 

The  results  of  the  Hardness  tests  at  high  temperatures  are 
summarised  in  Fig.  36. 

B.    PROPERTIES  OF  OTHER  ALLOYS,  GIVEN  FOR  REFERENCE 
IN  A  SUPPLEMENTARY  SECTION 

(1)  ALLOYS  OF  ALUMINIUM  AND  ZINC. 

(a)  Aluminium-Zinc  Alloys.  The  alloys  of  this  group,  which 
are  easily  utilised,  are  those  corresponding  with  the  shaded 
portion  of  the  fusibility  curve  of  aluminium -zinc  alloys  (Fig.  37). 
These  are  alloys  containing  0  to  30  %  zinc. 

The  following  table  due  to  Jean  Escard*  summarises  the 
properties  of  chill  cast  bars,  of  bars  forged  at  350°,  and  of 
bars  annealed  at  300°  for  one  hour  after  forging : — 


Tensile 

Elastic 

Alloy 

Strength 

Limit 

Elon- 

% 

% 

j-  r  c  aiiii  cut 

Kg       tons 

Kg      tons 

Bo/Lion 

Al. 

Zn. 

mm.  2      in.  a 

mm.2      in.2 

f     As  cast 

7-9      5-01 

4-2      2-67 

8-8 

94-7 

5-3 

}     Forged 

13-6      8-64 

11-3      7-18 

19-0 

V  Forged  &  annealed 

9-6      6-10 

2-5      1-59 

30-0 

Used  for  casting 

c     As  cast 

9-3      5-91 

6-5       4-13 

2-5 

and  rolling 

89-8 

10-2 

J     Forged 

18-2    11-56 

16-7    10-60 

33-5 

(  Forged  &  annealed 

14-8      9-40 

4-5      2-86 

38-0 

84-0 

16-0 

r     As  cast 
J      Forged 
V.  Forged  &  annealed 

17-1    10-86 
25-4    16-13 
23-2    14-73 

10-4      6-60 
18-1    11-49 
7-5      4-76 

2-0 

23-0 
28-0 

\Used  especially 
j     for  casting 

f     As  cast 

18-4    11-68 

17-1    10-86 

1-0 

79-0 

21-0 

{      Forged 
\.  Forged  &  annealed 

31-3    19-87 
31-5    20-00 

22-4   14-22 
27-6    17-53 

14-0 
14-5 

f  Kosenhain  and 

75-0 

25-0 

Forged 

42-0    26-67 

89-0    24-76 

16-5 

\      Archbutt: 

v  Density  :  3-2 

All  these  alloys  are  brittle  and  fail  under  repeated  impact : 
the  brittleness  is  increased  by  rise  of  temperature.  For  ex- 
ample, the  breaking  of  gear  boxes  of  motors. 

EFFECT  OF  TEMPERATURE  (Rosenhain  and  Archbutt). 

The  Tensile  Strength  diminishes  very  rapidly  with  rise  of 
temperature.  The  Tensile  Strength  of  the  alloy  containing 
25  %  zinc  changes  from  43-3  kg.  per  sq.  mm.  (2749  tons  per 
sq.  in.)  at  the  ordinary  temperature  to  28-5  kg.  per  sq.  mm. 
(18-10  tons  per  sq.  in.)  at  100°,  and  the  rate  of  this  diminution 
increases  with  the  temperature. 

We  have  noted  in  Fig.  35,  referring  to  the  ternary  alloy 
aluminium-zinc-copper,  the  rapid  decrease  in  hardness  with  rise 

*  Jean  Escard,  "  L' Aluminium  dans  1'Industrie "   (Dunod  and  Pinat, 
1918). 


LIGHT  ALLOYS  OF  ALUMINIUM 


83 


150 

140 

130 

120 

110 

100 

90 

80 

70 

•  60 

5-0 

40 

30 

20 

10 

0 


£00  Kg. 


WOO  Kg? 


50        100 


150      200       250 
Temperature 


300      350      400  °C 


FIG.  36. — Hardness  of  Copper -Tin-Nickel-Aluminium  Alloy,  con 
taining  11  %  Copper,  3  %  Tin,  and  1  %  Nickel,  at  High 
Temperatures  under  500  and  1000  Kg.  load. 


TOO       80 
700i 


60 


40         20 


°C 

600 

500 
400 
300 

200 


Netting 


Point 


V 

m 


Industrial 
Alleys, 


0%Zn. 


'0         20        40        60        80      100.%  AT 
Fia.  37. — Melting-point  Curve  of  Zinc-Aluminium  Alloys. 


84  ALUMINIUM  AND  ITS  ALLOYS 

of  temperature.    The  Brinell  number  for  this  alloy  falls  from 

85  under  a  load  of  500  kg.  at  the  normal  temperature,  to  56 
under  the  same  load  at  100°. 

Cadmium  is  sometimes  added  to  alloys  of  aluminium  and 
zinc  (1-40  %  zinc)  (patented  by  Bayliss  and  Clark,  England) 
in  the  proportions  of  0-001  to  10  respectively,  an  addition 
which  confers  great  malleability,  and  facilitates  working  and 
stamping. 

At  other  times,  0-5  %  to  1  %  of  copper  is  added,  or  even 
2  %,  forming  for  aluminium-zinc  alloys  the  soldering  metal  of 
the  following  composition  :— 

Aluminium  .     88  % 

Zinc    .          .          .     10% 
Copper         .  2  % 

(b)  Zinc-Aluminium  Alloys.  Investigations  on  the  alloys 
rich  in  zinc  have  been  carried  out  by  Leon  Guillet  and  Victor 
Bernard.* 

The  following  alloys,  among  others,  were  studied : — 

(1)  Binary  zinc-aluminium  alloys  containing  1,  2,  3,  or  5  % 

of  aluminium. 

(2)  Ternary  zinc-aluminium-copper  alloys  containing  2  %  of 

aluminium  and  2,  4,  6,  or  8  %  of  copper ;  4  %  of  alu- 
minium and  2,  4,  6,  or  8  %  copper ;  8  %  of  aluminium 
and  4  %  of  copper  (German  type  of  alloy). 

The  following  results  were  obtained : — 

(1)  The  cast  alloys  are  of  no  value,  the  Elongation  and 

Shock  Resistance  being  approximately  zero. 

(2)  The  rolled  alloys  have  low  elongations  and  almost  no 

Shock  Resistance. 

Extruded  alloys  generally  have  considerably  increased 
elongations.  This  extrusion  gave  the  following  properties  for 
the  alloy  containing  8  %  of  copper  and  4  %  of  aluminium : — 

Tensile  Strength  =30  to  31  kg.  per  sq.  mm.  (19-05-19-68  tons 

per  sq.  in.) 

%  Elongation      =27-29 
Shock  Resistance =2  kg.  m.  per  sq.  cm. 

This  is  the  most  interesting  of  the  zinc -aluminium  alloys,  but 
its  Shock  Resistance  is  very  low. 

*  "  Revue  de  Mdtallurgie,"  Sept.-Oct.,  1918. 


LIGHT  ALLOYS  OF  ALUMINIUM  85 

(2)  ALUMINIUM-TIN  ALLOYS. 

The  alloy,  containing  3  %  of  tin,  having  a  density  3-25, 
should  be  mentioned,  as  it  is  very  suitable  for  casting. 

Tin  is  frequently  added  in  foundry  practice,  in  order  to  facili- 
tate the  casting  of  alloys. 

(3)  ALLOYS  OF  ALUMINIUM  AND  MAGNESIUM. 

It  is  clear  that  these  alloys,  from  the  point  of  view  of  light- 
ness, are  more  important  the  more  magnesium  (density  :  1-75) 
they  contain. 

(a)  Aluminium-Magnesium  Alloys.  Magnalium,  which  con- 
tarns  5-25  %  of  magnesium,  has,  for  an  average  content  of 
magnesium,  a  density  of  about  2-80  in  the  cast  state. 

MECHANICAL  PROPERTIES  OF  ALUMINIUM-MAGNESIUM  ALLOYS. 

Jean  Escard,  in  the  work  just  quoted,  gives  the  following 
values  for  alloys  containing  2  %  and  10  %  of  magnesium  : — 

Tensile  Strength  Elonga- 

Magnesium  Treatment  • A s  tion 

Kg./mm.*          Tons/in/ 


0' 
.0 


10% 


Sand  cast      .          .          .      12-6  8-00  3 

Cast  and  rapidly  cooled  .     20-1  12-76  2 

Cast  and  quenched          .     28-1  17-84  1 

Sand  cast      .                    .15  9-52  2-4 

Cast  and  rapidly  cooled  .     23-6  14-99  3-4 

Cast  and  quenched          ,     43  27-30  4-2 


The  effect  of  quenching  on  alloys  containing  magnesium  is 
marked,  but  we  shall  discuss  this  more  fully  in  connection  with 
the  alloys  of  the  second  group  (light  alloys  of  great  strength). 
A  very  small  quantity  of  magnesium  (0-5  to  1  %)  is  sufficient 
to  increase  the  hardness  after  quenching  in  a  most  remark- 
able manner  ;  the  presence  of  30  %  to  50  %  of  magnesium 
renders  the  alloy  hard  and  brittle. 

(b)  Magnesium-Aluminium  Alloys.  The  magnesium-alu- 
minium alloys,  that  is  to  say,  alloys  rich  in  magnesium,  have 
been  worked  out  by  the  Germans  during  the  war,  and  the 
Zeppelin  L  49,  brought  down  at  Bourbonne,  possessed  several 
parts  made  of  similar  alloys.  The  alloy  would  be  of  the  type 
"  Elecktron,"  known  before  the  war,  whose  density  is  1-8, 
and  whose  conductivity  is  of  the  same  order  as  that  of  zinc  ; 
it  contains  90-92  %  of  magnesium. 

These  alloys  are  very  difficult  to  roll,  and  generally  contain 
numerous  holes  and  flaws. 


86  ALUMINIUM  AND  ITS  ALLOYS 

The  alloy  containing  90  %  of  magnesium  and  10  %  of 
aluminium  possesses  the  following  properties,  as  cast : — 

Elastic  Limit        =  8  kg.  per  sq.  mm.  (5-08  tons  per  sq.  in.) 
Tensile  Strength  =  1 1  kg.  per  sq.  mm.  (6-98  tons  per  sq.  in.) 
%  Elongation      =1 
Shock  Resistance = zero 

Their  most  striking  property  is  lightness,  and  they  should 
not  be  overlooked  by  aviation  authorities,  who  should  take  an 
interest  in  perfecting  their  manufacture. 

MICROGRAPHY  OF  CASTING  ALLOYS  OF  ALUMINIUM. 

The  five  photographs  in  Plates  III  and  IIlA  show  the 
micrographic  appearance  of  the  five  casting  alloys  of  aluminium 
that  have  been  studied. 

The  first  three  refer  to  aluminium-copper  alloys.  These 
alloys  contain  the  constituent  77  (this  being,  as  we  have  seen, 
pure  aluminium  or  a  solid  solution  of  copper  and  aluminium 
with  a  very  low  content  of  copper)  plus  the  eutectic  (CuAl2-h??). 

Photograph  1,  Plate  III,  referring  to  the  alloy  containing 
4  %  of  copper,  shows  solution  77  almost  pure.  Photographs  2 
and  3,  Plate  III,  referring  to  alloys  containing  8  %  and  12  % 
of  copper  respectively,  show,  to  a  slight  extent,  the  eutectic 
previously  described. 

Photographs  4  and  5,  Plate  H!A,  refer  to  the  ternary  and 
quaternary  alloys  containing  about  3  %  and  11  %  of  copper 
respectively. 


PLATE   III. 


-~^<*.-.<    \ 


PHOTOGRAPH  1. 
Copper,  4  %  ;  Aluminium,  96  %. 


/  -^ 


& 


PHOTOGRAPH  2. 
Copper,  8  % ;  Aluminium,  92  %. 


:.•»&' 

^ 

PHOTOGRAPH  3. 
Copper,  12  % ;   Aluminium,  88  %. 


To  face  page  86 


PLATE  IIlA. 


.'-,~:;-''V  .; 
"•  :  •&    VX-  -. 


PHOTOGRAPH  4. 

Copper,  3  °0  ;  Zinc,  12  %  ; 

Aluminium,  85  °0. 


PHOTOGRAPH  5. 

Copper,  1  1  °0  ;  Tin,  3  %  ;  Nickel,  1  %  ; 
Aluminium,  85  °0. 


To  face  page  86 


PART  IV 
LIGHT  ALLOYS  OF  GREAT  STRENGTH 

THE  group  of  light  alloys  of  great  strength  comprises  complex 
alloys  containing  copper,  magnesium,  manganese,  and  zinc,  in 
addition  to  the  aluminium ;  iron,  silicon,  and  alumina  are 
present  as  impurities,  having  been  introduced  with  the  alu- 
minium. 

These  alloys  have,  as  a  rule,  the  following  typical  com- 
positions : — 

ALUMINIUM-COPPER-MAGNESIUM  ALLOYS. 

Copper  .          .         .         .  "      .          .     3-5-4  % 

Magnesium     .         ...         .    about  0-5  % 
Manganese      .         .         .       '  .         .     0-5-1  % 
Aluminium  and  impurities         .         .  (difference) 

ALUMINIUM-COPPER-ZlNC-MAGNESIUM   ALLOY. 

Copper  .         .         .         .  .  .     2-5-3% 

Zinc      V        .         .         .  .  .     1-5-3% 

Magnesium     .  •       »         .  .  .     0-5  % 

Manganese      .  •     '  *          .  .  .     0-5-1  % 

Aluminium  and  impurities  .  .  (difference) 

The  remarkable  property  of  hardening  after  cooling,  which 
these  alloys  possess,  is  due  to  the  presence  of  the  magnesium, 
or  of  the  magnesium  and  zinc.  This  hardening  is  more  pro- 
nounced as  the  cooling  is  more  rapid.  The  mechanical  proper- 
ties, which  the  alloy  possesses  immediately  after  more  or  less 
rapid  cooling,  are  changed  completely  after  a  certain  interval 
of  time.  Without  entering  into  a  detailed  discussion  of  the 
causes  which  bring  about  this  transformation,  we  will  study 
from  a  practical  point  of  view,  the  results  obtained  by  mechani- 
cal work  and  thermal  treatment  and  from  them  deduce  useful 
practical  conclusions. 

Tests  have  been  carried  out  on  light  alloys,  aluminium- 
copper-magnesium,  having  the  average  composition  already 
given  and  corresponding  with  the  light  alloy  known  as 
duralumin. 

87 


88  ALUMINIUM  AND  ITS  ALLOYS 

A  description  of  this  work  is  given  in  the  following  form  : — 

Chapter  I.  (a)  Variation  in  the  mechanical  properties  (Tensile 
Strength,  Elastic  Limit,  Elongation,  Shock  Resistance, 
and  Hardness)  with  the  amount  of  cold  work,  (b) 
Variation  in  these  mechanical  properties  with  annealing 
temperature  (after  cold  work). 

Chapter  II.  Quenching — Quenching  Temperature,  Rate  of 
Cooling,  and  Ageing  after  Quenching. 

Chapter  III.    Reannealing  after  Quenching. 
Chapter  IV.     Cupping  tests,  after  thermal  treatment. 
Chapter  V.    High  temperature  tests. 


CHAPTER  I 

(a)  VARIATION  OF  THE  MECHANICAL  PROPERTIES  (TENSILE 
STRENGTH,  ELASTIC  LIMIT,  ELONGATION,  SHOCK  RESIS- 
TANCE, AND  HARDNESS)  WITH  THE  AMOUNT  OP  COLD 
WORK. 

TEST  pieces  were  cut  from  sheets,  10  mm.  thick,  subjected 
to  the  required  degree  of  cold  work  under  the  conditions 
already  stated  (see  Fig.  38). 


15 


MOi 
•100- 


FIG.  38.— Tensile  Test  Piece  (thick  sheet). 


20 


10 


-100- 


FIG.  39.— Tensile  Test  Piece  (thin  sheet). 

Test  pieces  were  also  prepared  from  thin  sheet  (see 
Fig.  39). 

This  research  was  carried  out  upon  metal  which  had  been 
annealed  in  a  bath  of  sodium  nitrite  and  potassium  nitrate 
at  450°  C.,  and  cooled  in  air.  The  reason  for  this  initial  treat- 
ment will  be  discussed  later. 

In  its  annealed  condition  the  alloy  possessed  the  following 
properties : — 


Tensile  Strength 
Kg/mm  *  Tons  /in  * 

Elastic  Limit 
Kg/mm  *  Tons  /in  * 

Elongation 
% 

Shock 
Resistance 
Kg.m/cms 

Longitudinal 
Transverse 

32           2032 
26           16-51 

13           8-25 
12           7-62 

18 
10 

3 
2-5 

90 


ALUMINIUM  AND  ITS  ALLOYS 


The  variations  in  these  properties  with  the  amount  of  cold 
work  are  shown  in  Figs.  40  and  41. 

Discussion  of  Fig.  40  (test  pieces  cut  longitudinally  to 
direction  of  rolling). 

Tensile  Strength.  This  property  decreases  to  a  minimum 
at  15-20  %  cold  work,  and  then  slowly  increases. 


DURALUMIN 
( Longitudinal) 


XU3 
C 
_0 

LU 


Kg.m  6 
per 


28 


24 


20          y  ' 

K 

12         \ 

\        /0 


Tensile  Strength^ 
Elastic  Limit 


Elongation 


Resistance    "**-: 


10  20  30 

%Co!d  Work 


15 


<0 

10  a 

V) 

c 
o 


40 


0° 


FIG.  40. — Variation  in  Mechanical  Properties  (Tensile  and 
Impact)  with  Cold  Work.  Metal  previously  annealed 
at  450°  and  cooled  in  air. 


Elastic  Limit.  This  increases  and,  after  20  %  cold  work, 
is  nearly  equal  to  the  Tensile  Strength. 

Elongation.  This  decreases  very  rapidly,  falling  from  18  % 
to  4  %  as  the  cold  work  increases  from  18  %  to  20  %.  The 
value  remains  constant  from  20  %  to  40  %  cold  work,  and 
finally,  at  50  %  cold  work,  becomes  extremely  small  (less  than 
1  %)• 

Shock  Resistance.  This  falls  from  3  kg.  m.  per  sq.  cm.  to 
less  than  1  kg.  m.  per  sq.  cm.,  while  the  cold  work  changes 
from  0  to  50  %. 


VARIATION  IN  MECHANICAL  PROPERTIES      91 

Fig.  41  (test  pieces  cut  transversely  to  direction  of  rolling). 
The  same  general  remarks  apply,  but  there  is  an  inflexion 
in  the  Elongation  curve. 

CONCLUSIONS. 

For  sheets  of  thickness  10  mm.  or  above,  cold  work  to  the 
amount  of  50  %  seems  to  be  the  maximum  possible  ;  further 

DURALUMIN 


Kg 

36                                (Transverse) 

per 

mrrr 

32 

20 

28 

Tensile      /» 

XX^^                                            Strength^? 

c 

24  ^^^^^    .s*  —  in  ^ 

15 

0 

*****~?2~~~'       Elastic  Limit 

rf 

20                       ,'" 

CM 

no 

s 

c 

c 

s 

O 

7 

s 

£. 

(J 

16     / 

10  Q. 

0^ 

s 

(/) 

/ 

E 

Kg.m6 

12 

^ 

per 

cm2  5 

V 

4 

8\  %  Elongation 

5 

X 

3 

...      V\. 

2 

4"  \. 

Shock      "***ri?'*».^                                     ,.'*^ 

1 

0 

o                                                   ""*  

0 

0                 10                20                30               40               5C 

%Cold  Work 

FIG.  41. — Variation  in  Mechanical  Properties  (Tensile  and 
Impact)  with  Cold  Work.  Metal  previously  annealed 
at  450°  and  cooled  in  air. 

work  beyond  this  point  leads  to  a  cracking  of  the  sheets. 
Moreover,  a  stronger  plant  is  required  than  that  usually 
employed  for  working  this  alloy — a  point  which  does  not 
arise  in  the  working  of  thin  sheets. 

(6)  VARIATION    OF    THESE    MECHANICAL    PROPERTIES    WITH 
ANNEALING  TEMPERATURE. 

The  material,  upon  which  these  tests  were  carried  out, 
had  been  cold  worked  to  the  extent  of  50  %,  and  test  pieces 
were  cut  from  it  longitudinally  and  transversely  to  the 
direction  of  rolling.  Up  to  300°  C.  the  metal  was  annealed 


92 


ALUMINIUM  AND  ITS  ALLOYS 


in  oil  and  from  300°  to  500°  C.  in  the  nitrate-nitrite  bath. 
Since  the  rate  of  cooling  has  an  effect,  which  will  be  discussed 
later,  two  standard  rates  have  been  used : — 

(i)  Cooling  very  slowly  in  the  furnace  or  liquid  bath  itself 

(100  degrees  per  hour  maximum  rate), 
(ii)  Cooling  in  air. 

The  metal  was  allowed  to  age  for  eight  days  after  cooling 
before  being  tested. 


DURALUMIN 

Kegr 

(Longitudinal) 

mm? 

32 

20 

%  Elongation 

28                                                                    ^~ 

Tensile    /^ 

Strength/ 

Kg. 

Elastic^         ^^v^./ 

1  5 

100 
90 
80 

^ 

per 

cm? 
9 

8 

20                       Limit  \           x^\ 
\        /%  \ 

\     '.Elongation         /• 

16                        \!       \    / 

CM. 

C 

10    | 

%    70 
I    60 
Z     50 
1     40 

7 
6 
5 
4 

_Brjnell  <  woo  Kg.)              i              >^"//..-- 
i"?i-  —  Hardness  \  1  \            ...-•"" 
12     .C500/rg.>       \'  \    ,-~:\     ....,<->• 

^tY  -#' 

s                    i  -4  v  \ 

M 

1 

5 

CO     30 

3 

//  w 

20 

2 

4                                 y  /SAocft 

10 

1 

^^f;^.*'  Resistance 

n 

0 

rt^"--""      7                       ... 

o 

100  200  300 

Annealing  Temperature 


400 


500  °C 


FIG.  42. — Variation  in  Mechanical  Properties  (Tensile,  Hardness, 
and  Impact)  with  Annealing  Temperature.  Metal  subjected 
to  50  %  Cold  Work,  annealed,  and  cooled  very  slowly. 

The  results  are  shown  in  Figs.  42,  43,  44,  and  45. 

Fig.  42,  Longitudinal,  Rate  of  cooling,  (i)  (furnace). 
Fig.  43  ,,  Rate  of  cooling,  (ii)  (air). 

Fig.  44,  Transverse      Rate  of  cooling,  (i)  (furnace). 
Fig.  45  „  Rate  of  cooling,  (ii)  (air). 

It  is  evident  from  these  figures,  that,  whatever  the  rate  of 
cooling  and  in  whatever  direction  the  test  pieces  ar$  cut, 


VARIATION  IN  MECHANICAL  PROPERTIES      93 


2ui  jod  stioj. 

o 


||ouug 


3  ui  uad  suoj_ 


CM    — 

J-LUO  jod  -ui  -9x 


94 


ALUMINIUM  AND  ITS  ALLOYS 


there  are  two  particularly  interesting  annealing  temperatures, 
i.e.  (1)  350°-375°,  (2)  475°-500°. 

The  following  table  summarises  the  results  obtained  on 
the  longitudinal  test  pieces  for  these  temperatures,  after  50  % 
cold  work : — 


Anneal 

Tensile  Strength 

Elastic  Limit 

Shock 

Temperature 

Rate  of 

Kg.             tons 

Kg.            tons 

tion 

Resistance 
Kg.m. 

(degrees  C.) 

Cooling 

mm.4            in.8 

mm.2          in.* 

% 

cm.8 

350 

(i) 

20           12-7 

6             3-81 

20 

6 

(ii) 

20           12-7 

7             4-45 

20 

4-5 

475 

(i) 

28           17-78 

12           7-62 

16 

4 

(ii) 

32           20-32 

18           11-43 

18 

4 

DURALUMIN 


Kg.  per                     (Transverse) 

mm.2 

32 

20 

c 

28 

o 

+J 

I 

Tensile.  / 

15 

5A.  --_-«..         """--"^^         Strength/ 

LJ 

"^^     ^v                  / 

UJ 

20                     Elastic\         \         I 
Limit  \          \       / 

c 

^          ^-^ 

'jr 

\ 

<D 

16                                                  x 

10Q, 

\ 

(0 

\ 

C 

6 

12                                                      \                         ^X' 

£ 

5 

•X  *        ^%N          / 

§4 

la 

8                                             /       \          Svv^-^"X 

%  Elongation:        \      ,'             ^ 

!       **^         ^/ 

5 

E2 

4                                     /   ,'*Shock~*'~*'--''' 

*;. 

/  /  Resistance 

---.".---.-.-*•-<.''' 

/% 

0                100              200              300              400             500  °C 

Annealing  Temperature 

FIG.  45.  —  Variation  in  Mechanical  Properties  (Tensile  and 
Impact)  with  Annealing  Temperature.  Metal  subjected 
to  50  %  Cold  Work,  annealed  and  cooled  in  air. 


It  is  clear  that  these  two  temperatures  correspond  with 
maxima  and  minima  of  the  tensile  properties  :  — 


VARIATION  IN  MECHANICAL  PROPERTIES      95 

350°  anneal.    First  maxima  of  the  Elongation  and  Shock 

Resistance. 
Minima  of  Tensile  Strength  and  Elastic  Limit. 

475°  anneal.    Second  maxima  of  the  Elongation  and  Shock 

Resistance. 
Maxima  of  Tensile  Strength  and  Elastic  Limit. 

The  anneal  at  350°  C.  may,  therefore,  be  described  as  a 
softening  anneal,  producing  maximum  ductility  in  the  metal. 
The  anneal  at  475°  C.  will  be  considered  side  by  side  with 
Quenching  Phenomena  in  the  following  chapter. 


CHAPTER  II 
QUENCHING 

(a)  CRITICAL  POINTS. 

A  RESEARCH  on  the  critical  points  of  alloys  of  the  duralumin 
type  has  been  carried  out  by  Chevenard,  using  a  differential 
dilatometer.* 

Fig.  46  shows  the  results  obtained  on  comparing  duralumin 
with  pure  aluminium. 


502° 


FIG.  46. — Duralumin  compared  with  pure  Aluminium, 
using  Dilatometer. 


The  dilatometric  method  evidently  gives  no  indication  what- 
ever of  critical  points  in  this  alloy.  On  the  expansion  curve 
there  is  no  sign  of  any  definite  irregularity. 

Since  there  is,  therefore,  no  a  priori  evidence  marking  out 
one  limiting  range  of  temperature,  it  is  necessary  to  carry 
out  a  complete  series  of  quenching  experiments  for  all 
temperatures. 

(6)  VARIATION  OF  MECHANICAL  PROPERTIES  WITH  QUENCHING 
TEMPERATURE  . 

Omitting,  for  the  present,  the  detailed  discussion  of  the 
effect  of  time  after  quenching,  the  following  procedure  has  been 
adopted. 

Tensile  and  shock  test  pieces  were  cut  longitudinally  from 

*  For  details  of  the  use  of  this  apparatus,  see  "  L'Acier,"  by  Lt.-Col. 
Grard  (Berger-Levrault),  1919. 

96 


QUENCHING 


97 


sheets  of  10  mm.  thickness,  and  possessed  after  rolling,  i.e. 
in  the  cold- worked  condition,  the  following  properties  : — 

24  kg. /mm.8  or  15-24  tons /in.2 
.  23  kg./mm.2  or  14-60  tons/in.2 
.  5 

2  kg. m. /cm.2 


Tensile  Strength 
Elastic  Limit    . 
%  Elongation  . 
Shock  Resistance 


The  test  pieces  were  heated,  preparatory  to  quenching,  in 
a  liquid  nitrate-nitrite  bath  to  the  following  temperatures  : 
300°,  350°,  400C 


>   450°,  500°,  and  550°  C. 
DURALUMIN 


32  Kg.  p«p 

20 

mm2 

70 

28 

%  Elongation 

60 

24 

15 

Tensile  Strength 

50 

$o"~        ^  •»•••  

s. 

_.••*          D  /"//?£//               *"""""*^'*""-.-..v.*?Z/.  

Ci 

I 

..-••'       Hardness 

c: 

|40 
|N 

Kg. 
m 

cP# 
3 

•~7W           ~~E/astic  Limit 
Y2         ^  ^Elongation  . 

10   | 

4 
| 

CO 

,**^"" 

^.  ••,                                       f\ 

20 

: 

8                          \                            ^X 

5 

Resistance 

10 

i 

4 

0 

u 

o            . 

°Days 

02468 

Time  after  Quenching 

FIG.  47. — Variation  in  Mechanical  Properties  with  Time 
after  Quenching  (from  300°). 

Figs.  47-52  (inclusive)  summarise  the  results  obtained 
after  quenching  in  water  at  20°  C. — which  we  will  call  rate 
of  cooling  (iii) — the  tests  being  carried  out 

Immediately  after  quenching 
48  hours       „ 

4  days         ,, 

5  days         ,, 
8  days         „ 


98 


ALUMINIUM  AND  ITS  ALLOYS 


Fig.  53  shows  the  variation  of  mechanical  properties  with 
quenching  temperature  after  a  uniform  ageing  of  eight  days. 

NOTES. 

(I)  Influence,  of  Time. 

The  effect  of  the  interval  of  time  after  quenching  is  noticeable 
from  a  temperature  of  300°  upwards,  and  is  particularly 
marked  above  400°. 


DURALUMIN 


70 


80 


50 


Kg.m  H 
per  cm2 


10 


32  Kg.  per 


28 

%  Elongation 

24 


Tensile  Strength 


7000  Kg. 

Brinell  No. 

500  Kg.-...- 


20 


15 


2  4  .  v;    6 

Time  after  Quenching 


8  Days 


FIG.  48. — Variation  in  Mechanical  Properties  with  Time 
after  Quenching  (from  350°). 

(2)  Influence  of  Temperature. 

From  200°  upwards,  certain  molecular  changes  take  place 
and  Fig.  63  reveals  two  particularly  noticeable  quenching 
temperatures,  350°  and  475°,  producing  the  following  properties 
in  the  metal : — 

Quenching  from  350° 

Tensile  Strength     .          .     20  kg./mm.2  or  12-7  tons/in.2 

Elastic  Limit          .          .       9  kg./mm.2  or    5-61  tons/in.2 

%  Elongation        .          .15 

Shock  Resistance  .         .       3  kg.m./cm.2 


QUENCHING 


99 


0                                 0 
N                                     CM 

2--UI  tied  SUOJL 

!2                 2                  *> 

o 

|      \ 

\       ^"e*     \    «S.^ 

§i  \ 

§               0 

0 
CO 

0 

o 

*t              m             ct             r~ 

CO  CM 

•LUO  add  LU 


O 

0 

o 
o> 

o 
00 

o 
1^ 

o 

(O 

0 
10 

o 

^«- 

o 

co 

o 

CM 

o 

o 

0         * 


100 


ALUMINIUM  AND  ITS  ALLOYS 


2ui  tied  SUOJL 


I 

ii 

uji 

K\ 


8 


II 

»ll 


'ill' 


z"! 

ID 


O 

:>     LJ       O 

O 
CD 

0 

O                ° 

§       § 

.  § 

0 

^     o\° 


||9uug 


E  t 


CD 

£  • 


Q.O 


if 

r 


QUENCHING 


Tensile  Strength     . 
Elastic  Limit 
%  Elongation 
Shock  Resistance  . 


Quenching  from  475° 

.  40  kg. /mm.2  or  25-4  tons /in.2 

.  20  kg. /mm.2  or  12-7  tons /in.2 

.  20 

.-  3-5kg.m./cm.2 


Remembering  that  quenching  is  nothing  more  than  heating 
followed  by  very  rapid  cooling  (rate  iii),  it  is  evident  that,  in 


DURALUMIN 


100 


90 


SO 


1 


70 


60 


\     50 

£. 

GO 


Kg.m 

Per2 
cm. 


3BC 


IK 


40  Kg  per 


mm 


36 

%  Elongation 
32 


23 


24 


Brinell  v-.... 

Hardness.. """       ^""-'.'.'.' 

.*••*""  V 


1  6      .....-• (500  Kg} 


12 


// 

v-.  / 

A      M 

/  v'-y--' 
./x^y 

8    ^//oc/f  Resistance //„*'' 

L"  ----y 

-    xo  Elongation 


100  200  300  400 

Temperature 


500 


25 


20 


10 


600°C 


FIG.  53. — Variation  in  Mechanical  Properties  with  Quenching 
Temperature  (after  8  days). 


this  chapter  and  the  preceding  one,  we  have  studied  the 
variations  of  the  worked  alloy  with  the  temperature  of  annea' 
after  cold  work,  and  with  the  rate  of  cooling  following  this 
anneal.  The  anneals  at  350°  and  475°  have  been  pointed 
out  as  being  especially  interesting,  whatever  the  rate  of  cooling. 


1X>*2       ;    :  v.AIiUMINIUM  AND  ITS  ALLOYS 

The  following  table  gives  a  summary  of  the  results  :— 


Anneal 

Tensile  Strength 

Elastic  Limit 

Elonga- 
tion 

% 

Shock 
Resistance 
Kg.m. 
cm.* 

Temperature 
(degrees  C.) 

Bate  of 
Cooling 

Kg.          tons 
mm.3          in." 

Kg.         tons 
mm.4         in.a 

350° 

(i)(100°p.h.) 
(ii)  (air) 
(iii)  (quenched 
in  water) 

20        12-7 
20       12-7 
20       12-7 

6        3-81 
7        4-45 
9        5-61 

20 
20 
15 

6 
4-5 
3 

475° 

(i)(100°p.h.) 

(ii)  (air) 
(iii)  (quenched 
in  water) 

28       17-78 
32       20-32 
40       25-4 

12       7-62 
18       11-43 
20       12-7 

16 
18 
20 

4 
4 
4 

These  two  annealing  temperatures  correspond  with  a  soften- 
ing treatment  and  a  final  treatment. 

The  treatment  which  yields  maximum  softening  consists 
in  annealing  at  350°,  and  cooling  very  slowly  (rate  (i),  furnace). 
The  final  treatment,  i.e.  that  which  gives  the  alloy  maximum 
strength,  consists  in  annealing  at  475°  and  cooling  extremely 
rapidly  (rate  (iii),  quenching  in  water).  Other  methods  of 
treatment — annealing  at  350°  followed  by  more  rapid  cooling 
(rate  (ii)  or  (iii)),  or  heating  at  475°  and  cooling  more  slowly 
(rate  (i)  or  (ii)) — serve  respectively  to  soften  and  harden  the 
metal  but  to  a  less  degree  than  the  two  treatments  mentioned, 
which  are,  therefore,  preferable. 

Finally,  Fig.  53  shows  that  quenching  from  above  550° 
produces  a  falling  off  in  all  properties.  Quenching  from  550° 
gives  the  following  properties  : — 

Tensile  Strength  .  .  27  kg./mm.2  or  17-14  tons/in.2 

Elastic  Limit  .  .  19  kg./mm.2  or  12-06  tons/in.2 

%  Elongation  .  .  2 

Shock  Resistance  .  .  2-5  kg.m./cm.2 

QUENCHING  OF  CAST  DURALUMIN. 

The  properties  of  cast  duralumin  are  as  follows  : — 
Sand  Cast. 

Tensile  Strength     .     (average)  1 1  kg.  /mm.2  or  6-98  tons /in.2 

%  Elongation        .     approx.  zero. 

Shock  Resistance  .     approx.  zero. 

Sand  Cast,  after  Quenching. 

Tensile  Strength     .     (average)  14  kg.  /mm.2  or  8-89  tons /in.2 
%  Elongation        .     approx.  zero. 
Shock  Resistance  .     approx.  zero. 


QUENCHING 

Chill  Cast. 

Tensile  Strength  (average) 
%  Elongation 
Shock  Resistance 


103 


10  kg. /mm.2  or  6-35  tons /in.2 
approx.  zero, 
approx.  zero. 


Chill  Cast,  after  Quenching. 

Tensile  Strength  (average) 
%  Elongation    . 
Shock  Resistance 


15  kg./mm.2  or  9-52  tons/in.2 
approx.  zero, 
approx.  zero. 


It  can  be  seen  that  unworked,  cast  duralumin  is  not  affected 
by  quenching. 


Kg.  per  mm.2 
r40 

%  Elongation 
36 


32, 


Brinell 
Number 

120 


110 
100 
90 
80 
70 
60 
50 
40 
30 
20 
10 


Kg. 
m 

per 

cm? 

9 


20 


10  o 


024     6     8    10  12  14  16  18  20  22  24  2»  28  SO  32  34  36  38  4O  42  44  46  413  5O  Hours 

Time  after  Quenching 

FIG.  54. — Variation  in  Mechanical  Properties  with  Time  after  Quenching 
from  475°  (during  first  48  hours). 


(c)  VARIATION  OF  MECHANICAL  PROPERTIES  WITH  DURATION 
OF  TIME  AFTER  QUENCHING. 

A  constant  temperature  of  quenching  has  been  chosen,  475°. 

Four  hundred  bars  of  duralumin  and  the  same  number  of 
shock  test  pieces  were  treated  simultaneously,  i.e.  heated  to 
475°  in  the  nitrate-nitrite  bath  and  quenched  in  water.  Tensi  e 
tests,  hardness  tests,  and  shock  tests  were  carried  out  under 
the  following  conditions  : — 


104 


ALUMINIUM  AND  ITS  ALLOYS 


1st  day    .     6  an  hour  throughout  the  24  hours. 
I  4  an  hour  during  the  first  12  hours, 
y   '  1  2  an  hour  during  the  second  12  hours. 
3rd  and  4th  days    .     2  an  hour. 
5th  6th,  7th,  and     I  2  2  hours. 

8th  days  J 

For  the  following  week    .     2  every  morning. 
For  the  next  fortnight     .     2  a  week. 

These  tests  can  be  continued  for  a  very  long  time  on  some 
test  pieces  kept  in  reserve. 

DURALUMIN 


130 
120 


m. 
per 

cm 

TOO  10 

c   00 
I 

OJ 
I    70 

r:  eo 
0 

.E   5°i 

"t 

CO 


20 
10 


Kg 


Kg.  per 

mm2 


40%  Elongation 


Tensile 
'Strength 


23 


24 


^ 


r\-.          ^  Elastic  Limit 

'  i'0x   fc~^- — -" 


x 


Hardness 


Resistance 


Hours 

~4O     50     60     TO     8*0     35~~i6o   tlo  1 4o  130  lio  1^6  1^0  1  f 0 


Pay* 


25 


20 


15.E 

(L 

o 

Q. 


3 


•01^34567 
Time  after  Quenching 

Fia.  55. — Variation  in  Mechanical  Properties  with  Time  after 
Quenching  from  475°  (during  first  8  days). 

VARIATION  DURING  THE  FIRST  EIGHT  DAYS. 

The  results  of  the  tests  during  the  first  twenty-four  hours 
are  accurately  shown  in  Fig.  54. 

Fig.  55  shows  the  results  for  the  first  eight  days.  Two 
distinct  periods  are  noticeable  : — 

(a)  First  four  days. 

(b)  Second  four  days. 


QUENCHING  105 

(a)  First  four  days. 

The  curves  for  this  period  are  characterised  by  very  marked 
oscillations,  which  cannot  be  attributed  to  experimental  errors, 
and  which  evidently  are  due  to  notable  molecular  changes. 

(b)  Second  four  days. 

During  this  period,  the  oscillations  become  less  pronounced, 
and  the  wavy  curves  flatten  out,  tending  to  an  equilibrium 

state. 

GENEBAL  FORM  OF  CURVES. 

The  following  conclusions  may  be  drawn  from  a  considera- 
tion of  the  general  form  of  the  curves  lying  most  evenly  through 
the  points. 

(1)  Tensile  Strength. 

The  Tensile  Strength  increases  in  an  oscillatory  manner, 
changing  from  30  kg.  per  sq.  mm.  to  38  kg.  per  sq.  mm.  (19-05 
tons/in2  to  24-13  tons/in.2)  in  the  first  four  days.  The  varia- 
tions during  the  last  four  days  are  included  between  the  limits 
of  38  to  40  kg.  per  sq.  mm.  (24-13  to  25-40  tons  per  sq.  in.). 
The  most  considerable  increase  occurs  during  the  first  ten 
hours  when  the  value  rises  from  30  to  36  kg.  per  sq.  mm. 
(19-06  to  22-86  tons  per  sq.  in.). 

(2)  Elastic  Limit. 

This  curve  is  of  the  same  general  form  as  that  of  the  Tensile 
Strength,  and  in  a  similar  manner  increases  from  10  to  23  kg. 
per  sq.  mm.  (6-35  to  14-61  tons  per  sq.  in.)  in  the  first  four  days. 
The  variations  during  the  last  four  days,  lie  between  the 
limits  of  22  to  24  kg.  per  sq.  mm.  (13-97  to  15-24  tons  per  sq.  in.). 
The  greatest  increase  occurs  during  the  first  twenty-one  hours 
when  the  value  rises  from  10  to  22  kg.  per  sq.  mm.  (6-35  to  13-97 
tons  per  sq.  in.). 

(3)  Elongation. 

The  Elongation  oscillates  very  considerably  during  the  first 
four  days,  but,  at  the  end  of  eight  days,  the  value  is  not  appre- 
ciably altered.  It  varies  about  a  mean  value  of  20  %. 

(4)  Shock  Resistance. 

The  same  remarks  apply  as  for  the  Elongation. 

(5)  Brinell  Hardness. 

The  curves  of  Hardness  under  a  load  of  1000  kg.  and  500  kg. 
respectively  are  similar  in  form  to  those  of  Tensile  Strength 
and  Elastic  Limit. 


106 


ALUMINIUM  AND  ITS  ALLOYS 


Brinell  No.  (1000kg.)  originally  80 

„          after  24  hours  110 
„          after  48  hours  100 

after  8  days  100 
(500  kg.)  originally  61 
„         after  24  hours  85 
„        after  48  hours  80 
„        after  8  days  75 

The  following  table  summarises  these  variations  : — 


Elastic  Limit 

Tensile  Strength 

Elonga- 
tion 

% 

Shock 
Resistance 
Kg.m. 
cm.8 

Ke. 

mm.3 

tons 
in.8 

Kg 

mm. 

tons 
in." 

Immediately  after 
quenching 
Four  days  after 
quenching 
Eight  days  after 
quenching 

10 

22 
22 

6-35 

13-97 
13-97 

30 

38 
38 

19-05 

24-13 
24-13 

20 

22 
20 

4-5 

3-4 
3-0 

VARIATIONS  AFTER  EIGHT  DAYS. 

A  further  investigation  of  the  variations  in  the  properties 
of  duralumin  with  the  length  of  time  after  quenching  can  be 
carried  out  on  the  test  pieces  which  were  kept  in  reserve. 

The  tests  carried  out  during  the  first  three  months  do  not 
reveal  any  important  variations  other  than  those  which  have 
been  already  noted  at  the  end  of  eight  days.  It  is  advisable, 
however,  to  continue  these  tests  for  a  very  long  period,  and 
on  a  very  considerable  number  of  test  pieces  to  minimise  the 
effect  of  individual  experimental  errors,  and  to  give  a  trust- 
worthy value  to  the  inferences  drawn  from  the  tests. 

While  these  systematic  tests  are  being  carried  out,  we  have 
attempted  to  find  an  alloy  of  high  strength,  prepared  as  long 
ago  as  possible,  whose  original  properties  had  been  accurately 
determined  and  whose  date  of  manufacture  was  definitely 
known. 

We  approached  the  firm  of  Breguet,  who  possess  samples 
taken  from  the  consignments  from  the  works  on  dates  definitely 
known.  Tests  had  been  carried  out  at  the  time  of  manufacture 
on  test  pieces  taken  from  the  samples.  It  must  be  noted  that 
these  samples  have  been  kept  in  store  and  there  is  therefore  no 
question  of  the  alloy  having  been  subjected  to  the  strain  of  flight. 

We  could  thus  see  how  the  alloy  had  behaved  during  storage 
and  investigate  whether  any  ageing  had  taken  place,  i.e.  an 
alteration  of  properties. 


QUENCHING 
The  following  table  summarises  the  results : — 


107 


Properties  as  determined  in 

Properties  as  determined  in 

Date 

original  tests 

Date 

final  tests 

Type  of    . 
Sample 

of 
Original 

Elastic 
Limit 

Tensile 
Strength 

Elon- 

of 
Final 

Elastic 
Limit 

Tensile 
Strength 

Elon- 

test 

tests 

Kg.    tons 

Kg.    tons 

jaiion 

% 

Kg.    tons 

Kg.     tons 

fallOn 

% 

mm.*     in.* 

mm.1    in,1 

mm.1   in.1 

mm.  *     in.  * 

Rectangular  tube 

25-0    15-87 

44-0    27-94 

17-8 

of  65/35  mm.. 

1916 

22        13-97 

37       23-49 

15 

Oct.  7 

23-3    14-80 

42-6    27-05 

11-05 

thickness  0-2  mm. 

1919 

23-0    14-60 

42-5    26-99 

— 

26-6    16-89 

44-0    27-94 

17-08 

Rectangular  tube 

—          — 

40       25-4 

20 

of  65/35  mm.. 

Mar. 

23-5    14-92 

38       24-13 

15 

25       15-87 

40       25-4 

17-3 

thickness  0-25  mm 

1918 

25       15-87 

37-5    23-81 

20 

25-3    16-07 

37-8    24-0 

20 

Torpedo  tube  of 

Oct. 

23-5    14-92 

39       24-76 

14 

tt 

26-6    16-89 

43-5    27-62 

17 

82/35  mm. 

1917 

26-6    16-89 

43-5    27-62 

15-2 

Bound  tube  of 

75  mm.  diam.. 

June 

24       15-24 

38       24-13 

14 

tt 

26        16-51 

41       26-03 

15-2 

thickness  0-2  mm. 

1916 

27       17-14 

44-6    28-32 

15-2 

Bound  tube  of 

55  mm.  diam.. 

Oct. 

23-5    14-92 

38       24-13 

14 

M 

29       18-41 

41        26-03 

15-2 

thickness  0-2  mm. 

1916 

28-6    18-16 

42-6    27-05 

15-2 

Bound  tube  of 

40  mm.  diam.. 

Oct. 

24       15-24 

38       24-13 

15 

m 

25       15-87 

41       26-03 

17-5 

thickness  0-1  mm. 

1918 

27-5    17-46 

40       25-4 

17-5 

This  table  shows  that  all  the  metal  of  this  consignment  has 
the  following  properties  : — 

Elastic  Limit      .  (23±1)  kg.  per  sq.  mm.  ((14-6±-63)  tons 

per  sq.  in.) 
Tensile  Strength.  (38 ±1)  kg.  per  sq.  mm.  ((24-13 ±-63)  tons 

per  sq.  in.) 
%  Elongation  .  14-5 ±0-5 

After  a  lapse  of  time  varying  from  one  to  three  years,  the 
properties  lie  between  the  following  limits  : — 

Elastic  Limit       .   (26  ±3)  kg.  per  sq.  mm.  ((16-51  ±1-9)  tons 

per  sq.  in). 
Tensile  Strength.  (41  ±3)  kg.  per  sq.  mm.  ((26-03 ±1-9)  tons 

per  sq.  in). 
%  Elongation  .  15-20. 

With  the  exception  of  one  test  piece  giving  1 1  -05  %  Elonga- 
tion, an  increase  in  the  value  of  all  the  properties  can  be 
observed. 

These  particular  tests,  then,  do  not  reveal  any  deterioration 
of  the  metal,  but,  on  the  contrary,  a  slight  general  improvement. 
In  order  to  draw  a  reliable  conclusion,  we  must  await  the  final 
results  of  the  methodical  experiments  now  in  hand — experi- 
ments in  which  the  values  of  the  original  properties  are  reliable 
on  account  of  the  number  of  the  tests  and  the  particular  care 


108  ALUMINIUM  AND  ITS  ALLOYS 

taken  in  carrying  them  out.  These  experiments  will  allow  us 
to  find  out  definitely  whether  there  is  any  gradual  improvement 
in  the  properties. 

VARIATION  or  THE  TIME  REQUIRED  TO  REACH  EQUILIBRIUM, 
WITH  THE  TEMPERATURE  AFTER  QUENCHING. 

The  preceding  tests  constitute  an  investigation  of  the  time 
required  to  reach  Equilibrium  after  quenching,  in  which  the 
changes  after  quenching  have  been  allowed  to  take  place  at 
the  normal  temperature.  The  effect  of  the  temperature  after 
quenching  on  the  attainment  of  Equilibrium  has  been  investi- 
gated by  means  of  supplementary  experiments. 

The  following  temperatures  were  employed  : — 

-  20°  C. 

0°C. 

+  20°  C. 

+  100°C. 

150° 

200° 

250° 

300° 

350° 

Immediately  after  quenching,  test  pieces  were  maintained 
at  each  of  these  temperatures  for  1,  2,  3,  4,  5,  and  6  hours 
respectively,  i.e.  some  at  —20°,  others  at  0°,  other  at  +20°,  etc. 

Tensile  tests  were  carried  out  after  each  of  these  periods  of 
time,  after  warming  up  or  cooling  to  air  temperature. 

The  results  can  be  summarised  as  follows  :— 

Temperature     —20°     After  six  hours  there  is  no  change  in 

properties. 

,,  0°     No  change  after  six  hours. 

,,  +20°     After  six  hours  the  Tensile  Strength 

has  increased  by  4  kg.  per  sq.  mm. 

(2-54  tons  per  sq.  in.)  to  the  value 

34  kg.  per  sq.  mm.  (21-6  tons  per 

sq.  in.). 
,,  100°     After  six  hours  the  Tensile  Strength 

has  increased  by  8  kg.  per  sq.  mm. 

(5-08  tons  per  sq.  in.)  and  become 

38  kg.  per  sq.  mm.  (24-13  tons  per 

sq.  in.). 
All  the  properties  have  attained  their 

mean  normal  values. 


QUENCHING  109 

Temperature       150°     All  the  properties  have  attained  their 

mean    normal    values    after    two 
hours. 

„  200°     The  process  is  simply  an  anneal  and 

and  above        the  rate  of  cooling  has  a  pronounced 

effect. 

The  results  obtained  are  strictly  con- 
cordant with  those  drawn  dia- 
grammatically  in  Fig.  57  (variation 
of  mechanical  properties  with  tem- 
perature of  reanneal  after  quenching 
from  475°). 

From  these  tests  the  following  conclusions  may  be  drawn  : — 
Changes  after  quenching  are  retarded  by  low  temperature. 
They  become  more  rapid  as  the  temperature  immediately 
after  quenching  is  raised  between  the  limits  of  0°  and  150°, 
temperatures  above  150°  causing,  after  similar  cooling  to  air 
temperature,  changes  in  the  properties.     If  the  alloy  be  im- 
mersed in  boiling  water,  for  example — a  very  practical  pro- 
cedure— Equilibrium  is  reached  much  more  rapidly. 

Immediately  after  quenching. 

Tensile  Strength  =30  kg.  per  sq.  mm.  (19-05  tons  per  sq.  in.) 
Elastic  Limit        =  10  kg.  per  sq.  mm.  (6-35  tons  per  sq.  in.) 
%  Elongation      =18 

After  immersion  in  boiling  water  for  one  hour  after  quenching. 
Tensile  Strength  =35-5  kg.  per  sq.  mm.  (22-54  tons  per  sq.  in.) 
Elastic  Limit  =17-5  kg.  per  sq.  mm.  (1 1-10  tons  per  sq.  in.) 
%  Elongation  =20 

After  immersion  in  boiling  water  for  two  hours  after  quenching. 
Tensile  Strength  =37  kg.  per  sq.  mm.  (23-49  tons  per  sq.  in.) 
Elastic  Limit  =  18-5  kg.  per  sq.  mm.  (5-40  tons  per  sq.  in.) 
%  Elongation  =20 

After  six  hours  under  these  conditions. 

Tensile  Strength  =37  kg.  per  sq.  mm.  (23-49  tons  per  sq.  in.) 
Elastic  Limit        =20  kg.  per  sq.  mm.  (12-7  tons  per  sq.  in.) 
%  Elongation      =20 

Values  which  remain  approximately  un- 
changed after  further  immersion  in  boiling 
water. 

Thus,  by  immersion  in  boiling  water  after  quenching, 
Equilibrium  is  reached  more  rapidly — an  effect  which  is  of 
interest  from  the  industrial  point  of  view. 


CHAPTER  III 


VARIATION   OF   MECHANICAL  PROPERTIES   WITH   THE 
TEMPERATURES   OF   REANNEAL  AFTER  QUENCHING 

THE  metal,  in  every  case  quenched  from  47 5° ,  was  reannealed 
at  a  series  of  temperatures — every  fifty  degrees  from  the 
normal  up  to  500° — and  cooled. 

The  three  rates  of  cooling  already  defined  were  employed : 
rate  (i),  cooling  very  slowly  in  the  bath  ;  rate  (ii),  cooling  in 
air  ;  rate  (iii),  cooling  by  quenching  in  water. 


Kg  per* 
mm2 


DURALUMIN 


25 


100  200  300  400  500° 

Annealing    Temperature 

FIG.  56. — Variation  in  Mechanical  Properties  with  Annealing  Tempera- 
ture.   Metal  quenched  from  475°,  reannealed,  and  cooled  very  slowly. 

110 


VARIATION  IN  MECHANICAL  PROPERTIES     111 

The  results  for  the  three  rates  of  cooling  are  shown  in  Figs. 
56,  57,  and  58  respectively. 

All  the  properties  show  a  minimum  at  a  temperature  which 
varies  with  the  rate  of  cooling  as  shown  in  the  following  table : — 


E  ate  of 
Cooling 

Temperature 
of  Minimum 

Values  corresponding  with  the  minimum 

Tensile  Strength 

Elastic  Limit 

Elonga- 
tion 

% 

Shock 
Resistance 

Kg.  in. 
cm.* 

Kg.             tons 
mm.*             in.* 

Kg.             tons 
mm.*             in.* 

(i) 
(") 
(iii) 

330°-360° 
290°-320° 
275°-300° 

20            12-7 
25            15-87 
24            15-24 

7            4-4 
11           6-98 
9           5-71 

14 
14 
14 

4-5 
5 
5 

These  minima  do  not  afford  any  particular  interest. 

DURALUMIN 
Kg.  per 


140 
130 

120 
no 

100V) 


GO 

505 

40 

30J3 

202 

10  1 


2.4jf/asf/c  Limit 

™"  *"-^ 


23 


20  (1000'KgT  /:\ 

.6..  Hardness 

GOO  Kg  j --..... 


ion 


.Shock 

Resistance 


\\\ 

\\ 

\\ 


100 


200 


25 


20 


15  c* 
c 

s. 
<D 

a. 

(0 

10  I 


300 


400 


500°C 


Annealing  Temperature 


FIG.  57. — Variation  in  Mechanical  Properties  with  Annealing  Tempera 
ture.     Metal  quenched  from  475°,  reannealed,  and  cooled  in  air. 


112 


ALUMINIUM  AND  ITS  ALLOYS 


Fig.   56.     Quenching  from  475°,  reannealing  followed  by 

very  slow  cooling  (rate  (i)). 

The  most  interesting  points  on  these  curves  correspond  with 
the  reannealing  temperature  400°. 
For  this  temperature  : — 

Tensile  Strength  =22  kg.  per  sq.  mm.  (13-97  tons  per  sq.  in.) 
Elastic  Limit        =7  kg.  per  sq.  mm.  (4-44  tons  per  sq.  in.) 
%  Elongation     =22 
Shock  Resistance=5  kg.  m.  per  sq.  cm. 

DURALUMIN 


130 
120 
110 


Kg 


':>etl 

:r 
TOO  10 


£ 


808 
70  7 


O 
.E     50  5 

£. 

00  404 
303 
202 
10  1 


Hardness ; 


16 


(SOOKg 


-^Elongation 

\\  \ 

V\   \ 
-... 

" 


12 
12 


Shoch 
Resistance 


20 


TOO  200  300  400 

Annealing    Temperature 


500°C 


Fio.  58. — Variation  in  Mechanical  Properties  with  Annealing  Tern- 
perature.  Metal  quenched  from  475°,  reannealed,  and  quenched 
in  water. 

This  is  a  softening  treatment,  giving  values  approximately 
equal  to  those  produced  by  the  softening  process  previously 
described  but  entailing  a  more  complicated  method  of  working. 


VARIATION  IN  MECHANICAL  PROPERTIES     113 

Fig.  57.     Quenching  from  475°,  reannealing,  followed  by 

cooling  in  air  (rate  (ii)). 
No  particular  advantage. 

Fig.  58.    Quenching  from  475°,  reannealing  and  quenching 
in  water  (rate  (iii)). 

The  most  interesting  values  are  those  corresponding  with 
the  range  of  annealing  temperatures  475°-500°. 

This  is  simply  a  process  of  double  quenching  and  gives  the 
alloy  the  following  properties  : — 

Tensile  Strength  =40  kg.  per  sq.  mm.  (25-4  tons  per  sq.  in.) 
Elastic  Limit        =23  kg.  per  sq.  mm.  (14-6  tons  per  sq.  in.) 
%  Elongation      =22 
Shock  Resistance=5  kg.  m.  per  sq.  cm. 

It  is  clear  from  these  values  that  a  double  quenching  is 
superior  to  a  single  one.  Two  quenchings  improve  the  Elastic 
Limit,  the  Elongation,  and  the*Shock  Resistance,  and  should 
therefore  be  employed  if  the  maximum  values  of  these  proper- 
ties are  required  in  the  finished  metal. 

CONCLUSION. 

From  the  practical  point  of  view,  this  type  of  light  alloy  can 
be  subjected,  after  cold  work,  to  three  treatments  : — 

(1)  Annealed  at  350°  and  cooled  very  slowly  (rate  (i)),  giving 

the  most  suitable  intermediate  state  from  the  point  of 
view  of  further  mechanical  work.  This  is  the  softening 
process. 

(2)  Annealed  at  475°  and  quenched,  yielding  the  hardened 

or  final  state. 

(3)  Annealed  at  475°,  quenched,  reannealed  at  475°-500°, 

and  quenched  again.  This  process — double  quenching 
— yields  the  optimum  final  state. 


CHAPTER  IV 

RESULTS   OF  CUPPING  TESTS   AFTER  VARYING 
THERMAL  TREATMENT 


THE  experimental  methods  were  the  same  as  those  described 
already  for  the  cupping  tests  on  aluminium  (page  41). 

The  circles  to  be  tested  were  taken  from  sheets,  2  mm.  thick, 
having  been  cold  worked  to  the  extent  of  40  %. 


DURALUMIN 
(Cupping     Tests) 


C    7 
O 

<o 
Q. 

£ 

~    5 
O 

jC 


D  K^ 

Breaking 
Load 

1500 


1400 


1300 


1200 


rate  djT~-- 
cooling 
(air) 


Ubo 


Tooo' 


900 


_ 

\(n  termed  ia 
rate  o 
coolihgjdif7"~~~ 


/Rapid 

i  cooling 

/(Quench) 


cooling 
(bath) 


300   325   350   375   400   425   450   475   500  °C 

Annealing  Temperature 

FIG.  59. — Variation  in  Breaking  Load  and  Depth  of  Impression  with  Annealing 
Temperature.    Anneal  followed  by  cooling  at  varying  rates  : 

— •— • •••  very  slow. 

—  — cooling  in  air  (intermediate  rate). 

— —   .   —   .    cooling  in  water  (Quenching ;  very  rapid). 

114 


RESULTS  OF   CUPPING  TESTS  115 

The  following  temperatures  of  annealing  after  cold  work 
and  the  following  rates  of  cooling  have  been  employed  : — 

Temperature  of  anneal :    300°,  350°,  400°,  450°,  475°. 
Rates  of  cooling  :   (i),  (ii),  and  (iii)  (as  previously  defined). 

Fifteen  circles  were  heated  at  each  of  the  above  tempera- 
tures, and  of  these,  five  were  cooled  very  slowly  (rate  (i)), 
five  in  air  (rate  (ii)),  and  five  quenched  (rate  (iii)). 

The  results  of  the  tests  are  shown  in  Fig.  59,  representing 
the  curves  for  the  breaking  loads  and  for  the  depths  of  impres- 
sion corresponding  with  the  different  rates  of  cooling,  plotted 
against  varying  annealing  temperature. 

The  general  shape  of  these  curves  shows  very  clearly  the 
remarkable  results  of  annealing  at  350°  and  cooling  very  slowly 
(rate  (i)).  This  treatment  gives  to  the  alloy  the  maximum 
ductility,  and  in  this  molecular  state  the  maximum  depth  of 
impression  is  produced. 

These  cupping  tests  confirm  the  preceding  tests,  and  we 
can  conclude  that  annealing  at  350°,  after  cold  work,  followed 
by  very  slow  cooling  (rate  (i)),  is  the  optimum  treatment  for 
softening  the  metal,  i.e.  for  producing  maximum  ductility  and 
maximum  malleability. 

Certain  cupping  tests  have  been  carried  out  on  sheets 
possessing  different  degrees  of  cold  work  (20-100  %)  under 
the  same  experimental  conditions,  i.e.  annealing  at  the  specified 
temperatures  and  cooling  according  to  the  three  rates  of 
cooling  mentioned. 

The  same  conclusions  were  arrived  at  as  in  the  case  of  40  % 
cold  work.  Furthermore,  the  final  values,  after  annealing  at 
350°  or  at  475°,  followed  by  variable  rates  of  cooling,  vary 
directly  with  the  amount  of  cold  work.  The  maximum  malle- 
ability is  thus  obtained,  for  thin  sheets,  by  cold  working  to  the 
amount  of  100  %,  and  annealing  at  350°  followed  by  very  slow 
cooling. 


CHAPTER  V 
HARDNESS  TESTS   AT  HIGH   TEMPERATURES 

HARDNESS  determinations  were  made  at  every  fifty  degrees 
up  to  600°  on  sixty  cylindrical  test  pieces,  20  mm.  long  and 
20  mm.  in  diameter.  The  pressure  used  was  500  kg. 

The  results  are  shown  in  Fig.  60,  which  should  be  considered 
side  by  side  with  those  obtained  under  the  same  conditions  for 
aluminium  and  casting  alloys. 


170 
180 
150 
140 
130 
120 

£.  110 

"I  10° 
Z  90 

?  80 

c 

i§  70 

60 

50 
40 
30 
20 
10 


0     50100150200         300         400          500 

Temperature 


600 


'700°C 


FIG.  60.— High  Temperature  Hardness  Tests  (500  Kg.)  on  Duralumin 
quenched  from  475°. 

116 


PART    V 

THE   CUPRO-ALUMINIUMS   OR  ALUMINIUM   BRONZES 

THE  cupro-aluminiums  considered,  from  an  industrial  stand- 
point, are  those  in  which  the  respective  amounts  of  the  con- 
stituents are  limited  to  the  part  of  Curry's  diagram  lying 
between  88  %  and  92  %  of  copper,  or  12  %  and  8  %  of  alu- 
minium, though  the  presence  of  other  constituents,  such  as 
manganese,  iron,  or  nickel,  may  cause  variations  in  these 
amounts. 

The  typical  alloy,  i.e.  the  alloy  containing  90  %  of  copper 
and  10  %  of  aluminium,  was  studied  in  a  very  thorough 
manner  by  H.  St.  Claire  Deville,  more  than  sixty  years  ago, 
at  which  time  it  was  still  a  precious  metal,  whose  cost  price 
was  about  32  francs  per  kilogramme  (lls.  9d.  per  lb.). 

Numerous  investigations  have  been  made  since  that  of 
St.  Claire  Deville,  particularly  by  H.  Le  Chatelier,  Campbell 
and  Mathews,  Guillet,  Breuil,  Gwyer,  Carpenter  and  Edwards, 
Curry,  Rosenhain,  and  afterwards  Portevin  and  Arnon. 

We  only  intend  to  discuss  the  particular  results  obtained 
for  three  special,  clearly  defined  alloys,  referring  for  questions 
of  a  general  nature  to  the  notable  works  mentioned  above. 
These  results  show  the  uses  to  which  these  alloys  can  be  put, 
and  the  properties  they  may  possess. 

These  alloys  fall  into  the  following  classes  : — 

Type  I.  Alloy  containing  90  %  of  copper  and  10  %  of 
aluminium. 

Type  II.  Alloy  containing  89  %  of  copper,  1  %  of  man- 
ganese, and  10  %  of  aluminium. 

Type  III.  Alloy  containing  81  %  of  copper,  4  %  of  nickel, 
4  %  of  iron,  and  11  %  of  aluminium. 

We  shall  summarise  the  results  of  this  investigation  in  the 
following  manner  : — 

Chapter     I.    General  properties  of  the  cupro-aluminiums. 
Chapter    II.     Mechanical  properties. 
Chapter  III.    Micrography. 

117 


CHAPTER  I 
GENERAL   PROPERTIES   OF  THE   CUPRO-ALUMINIUMS 

CHEMICAL  PROPERTIES. 

THESE  alloys  are  sufficiently  resistant  to  the  chemical  action 

of  liquids,  especially  sea  water. 

They  are  not  oxidised  at  high  temperatures,  which  renders 
them  particularly  suitable  for  the  direct  production  of  finished 
and  accurate  stampings. 

PHYSICAL  PROPERTIES. 

Colour.  The  alloys  are  yellow  or  slightly  green,  and  capable 
of  taking  a  high  polish. 

Density.  This  varies  with  the  percentage  of  aluminium. 
For  the  90/10  alloy,  it  is  about  7 -5  (Density  of  copper  =8-8 

,,          aluminium   =2-6) 

Aluminium  bronze  thus  has  an  advantage,  from  the  point  of 
view  of  weight,  over  60/40  brass,  whose  density  is  about  8-4, 
and  which  is  employed  for  some  of  the  same  purposes. 

Wear  and  Abrasion.  Cupro-aluminiums  or  aluminium 
bronzes  have  a  mineralogical  hardness,  which  is  retained  at 
relatively  high  temperatures,  as  we  shall  see  later.  Their 
sclerometric  or  "  scratch  "  hardness  is  great.  As  regards  wear, 
the  advantages  of  cupro -aluminium  are  unquestionable.  From 
the  point  of  view  of  abrasion,  cupro -aluminium  possesses  valu- 
able qualities,  and  its  coefficient  of  friction  is  low — it  possesses 
properties  approaching  those  of  antifriction  metals. 

Specific  Resistance.  As  soon  as  a  little  aluminium  is  added 
to  copper,  its  resistivity  is  increased.  The  Specific  Resistance 
of  cupro-aluminiums  is  shown  in  the  following  table,  which 
summarises  the  work  of  Pecheux.  It  is  expressed  in  microhms 
per  cm.  cube. 

A  luminium.    Value  of  Specific  Resistance  at  a  Temperature  t. 

3°  Rt=  8-26(1  +0-00102t+0-000003t2) 

5  Rt=  10-21(1  +0-00070t+0-000002t2) 

6  Rt=ll-62(l+0-00055t+0-000002t2) 
7-5  Rt=  13-62(1 -fO-00036t-}-0-000001t2) 

10  Rt=  12-61(1  +0-00032t+0-000002t2) 

94  Rt—  3-10(1  +0-00038t+0-000003t2) 

118 


GENERAL  PROPERTIES  119 

Electric  Permeability.  Very  low.  Cupro-aluminiums  may 
be  considered  to  be  almost  impermeable  and  non-magnetic. 

Foundry  Difficulties.  The  great  difficulty  lies  in  obtaining 
sound  ingots,  the  obstacles  being  the  large  contraction  of  the 
cupro-aluminium,  the  liberation  of  gases  at  the  moment  of 
solidification,  and  the  formation  of  alumina  which  is  difficult 
to  remove.  This  question  of  casting  has  been  the  subject  of 
investigation.  The  use  of  large  runners  feeding  the  ingot,  and 
the  stirring  and  skimming  of  the  surfaces  is  a  remedy,  which 
has  the  disadvantage  of  greatly  increasing  the  cost  price.  The 
economic  production  with  small  runners  and  the  avoidance  of 
skimming  can  be  carried  out  to-day  by  means  of  the  device 
for  casting  without  oxidation — Durville's  method. 

Suitability  for  Forging.  Aluminium  bronzes  can  be  forged 
very  easily  at  a  temperature  of  900°.  There  is,  therefore,  a 
very  much  greater  scope  for  forging  in  a  single  heating  than 
in  the  case  of  the  60/40  brasses,  which  have  only  a  limited 
range  of  temperature,  about  600°,  at  which  forging  is  possible. 
Furthermore,  with  certain  of  these  alloys,  as  we  shall  see, 
it  is  possible  to  obtain  after  treatment  results  distinctly  superior 
to  those  of  the  forgeable  brasses,  as  regards  Tensile  Strength 
and  Elastic  Limit  as  well  as  Elongation. 

Suitability  for  Casting.  The  malleability  of  aluminium 
bronzes  at  high  temperatures  and  their  freedom  from  oxidation 
makes  them  suitable  for  castings,  particularly  in  metallic 
moulds.  The  contraction  of  the  alloys  constitutes  a  difficulty 
which  can  be  overcome  by  the  skill  of  the  founder  and  a  suit- 
able arrangement  of  runners. 

Nevertheless,  the  suitability  for  forging  and  stamping  seems 
to  be  the  outstanding  characteristic  of  cupro-aluminiums,  and 
should  be  made  use  of  in  the  majority  of  cases. 

Use.  The  above  account  describes  the  forgeability,  freedom 
from  oxidation,  electric  impermeability,  and  the  resistance 
to  wear  and  abrasion,  which  result  in  the  use  of  the  alloy  for 
the  manufacture  of  pressed  articles,  of  wire  for  springs  and 
electrical  resistances,  and  of  electrical  apparatus. 


CHAPTER  II 
MECHANICAL   PROPERTIES 

THE  mechanical  tests  carried  out  were  : — 

(1)  Tensile  tests, 

(2)  Shock  tests, 

(3)  Hardness  tests, 

and  were  preceded  by  an  investigation  of  the  critical  points  by 
the  dilatometric  method. 

(1)  Tensile  Tests.    These  tests  were  carried  out  on  cylindri- 
cal bars,  13-8  mm.  in  diameter,  and  shaped  as  in  Fig.  61. 


• 

*^                                                |                                               V 

m^ 

wP       1.3-8 

25 

i 

*i*A 

FIG.  61. — Tensile  Test  Piece  (Round  Bars). 

(2)  Shock  Tests.    These  were  carried  out  on  test  pieces  of 
10  x  10  X  53  mm.  with  a  2-mm.  notch. 

(3)  Hardness  Tests.    These  were  carried  out  at  gradually 
increasing,  high,  temperatures,  under  a  load  of  500  kg.,  on 
cylinders   2  cm.  in   diameter   and   2   cm.  high,  using  a  ball 
10  mm.  in  diameter. 

The  test  pieces  were  taken  from  forged  or  cast  bars  ;  liquid 
baths  were  employed  to  heat  the  test  pieces,  and  the  tempera- 
ture accurately  regulated. 

Scheme  of  Work.  The  investigations  were  carried  out 
according  to  the  following  general  scheme  for  each  type  of 
alloy  considered,  with  simplifications  for  certain  types  :— 

(a)  Preliminary  chemical  analysis. 

(b)  Determination  of  curve  of  critical  points. 

(c)  Investigation  of  the  variation  in  mechanical  properties, 

with  temperature  of  anneal  after  casting  or  forging. 

120, 


MECHANICAL  PROPERTIES 


121 


(d)  Investigation  of  the  variation  in  mechanical  properties 

with  the  quenching  temperature. 

(e)  Investigation  of  the  variation  in  mechanical  properties 

with  temperature  of  reanneal  subsequent  to  quenching 
from  different  temperatures. 
(/)  Hardness  tests  at  ordinary  and  high  temperatures. 

I.    TYPE  I 

90  %  Copper— 10  %  Aluminium 

(a)  CHEMICAL  ANALYSIS. 

Copper       .          .        ....         ,89-15 

10-10 


Aluminium 

Manganese 

Iron 

Nickel 

Zinc 

Lead 

Tin  . 

Difference 


0-30 

0-25 

nil 

nil 

nil 

nil 

0-2 

100-0 


(b)  DETERMINATION  OF  CRITICAL  POINTS. 

These  critical  points  have  been  investigated  by  Chevenard 
and  the  results  are  shown  in  the  following  diagrams. 


-2 


Ar2 


FIG.  62. — Aluminium  Bronze,  Type  I. 

The  expansion  curves  show,  on  heating,  three  breaks,  Ac1} 
Ac 2,  Ac  8,  and  on  cooling  again  two  breaks,  AT!  and  Ar2  (see 
Fig.  62).  Whenever  the  alloy  is  heated  above  the  point  Acs, 
similar  phenomena  are  observed  on  cooling  again  ;  the  position 
of  the  points  ^i*  4^  appear  hardly  to  depend  upon  the  rate 


122 


ALUMINIUM  AND  ITS  ALLOYS 


of  cooling  (see  Figs.  63  and  64).    In  Fig.  64,  the  mean  rate  of 
cooling  is  half  that  represented  in  Fig.  63. 

If  the  temperature  does  not  reach  Ac3  (Fig.  65),  the  curve 
of  cooling  is  without  any  peculiarity. 


FIG.  63. — Aluminium  Bronze,  Type  I.    Allowed  to  cool 
in  Furnace. 


Ac- 


100200300 


Ac! 


600        700 


FIG.  64. — Aluminium  Bronze,  Type  I.     Slow  cooling. 


C2 

500       600       700, 


Ad 


FIG.  65.  —  Aluminium  Bronze,  Type  I.     Temperature 
not  exceeding  Ac3. 

(c)  VARIATION  IN  THE  MECHANICAL  PROPERTIES  OF  CUPRO- 
ALUMINIUM  (TYPE  I),  TENSILE  AND  IMPACT,  WITH  THE 
ANNEALING  TEMPERATURE. 


Alloy  as  Cast. 

The  variation  in  these  properties  are  summarised  in  Fig.  66. 
The  test  pieces  were  cooled  in  air  after  heating.  As  cast,  cupro- 
aluminium  (Type  I)  possesses  the  following  properties  :  — 


MECHANICAL  PROPERTIES 


123 


Tensile  Strength  =40  kg.  per  sq.  mm.  (25-4  tons  per  sq.  in.) 
Elastic  Limit        =26  kg.  per  sq.  mm.  (16-51  tons  per  sq.  in.) 


%  Elongation      =10 


Shock  Resistance  =  1  kg.  m.  per  sq.  cm. 

Annealing  has  a  particularly  advantageous  effect  on  the 
Elongation  and  Shock  Resistance,  so  that  after  annealing  at 
about  800°,  the  properties  have  the  following  values  : — 

Tensile  Strength  =52  kg.  per  sq.  mm.  (33-02  tons  per  sq.  in.) 
Elastic  Limit        =24  kg.  per  sq.  mm.  (15-24  tons  per  sq.  in.) 
%  Elongation      =22 
Shock  Resistance  =  5  kg.  m.  per  sq.  cm. 


80 
70 

60 

c 
O  50 

5 
xio 

I40 

UJ 
^  30 

20 
10 


Kg 

per 

mnr 


Tensile^ 
Strength 


'esfstance 


50 
45 
40 
35 

30  — 

<D 

25  a 
m 

20    O 
15 
10 
5 


0   100   200  300  400   500   600  700   800  900"C 

Annealing    Temperature 

FIG.  66. — Variation  in  Mechanical  Properties  (Tensile  and 
Impact)  with  Annealing  Temperature.  Cast  Aluminium 
Bronze,  Type  I  (Cu  90  %,  Al  10  %). 

(c2)  Alloy  as  Forged. 

The  variations  in  the  properties  are  summarised  in  Fig.  67. 
In  the  forged   state,  cupro-aluminium   (Type   I)  has  the 
following  properties  : — 

Tensile  Strength  =56  kg.  per  sq.  mm.  (35-56  tons  per  sq.  in.) 
Elastic  Limit        =32  kg.  per  sq.  mm.  (20-32  tons  per  sq.  in.) 
%  Elongation      =10 
Shock  Resistance=2  to  3  kg.  m.  per  sq.  cm. 


124 


ALUMINIUM  AND  ITS  ALLOYS 


Annealing  at  850°  especially  improves  the  Shock  Resistance 
and  Elongation,  whilst  lowering  the  Elastic  Limit : — 

Tensile  Strength  =55  kg.  per  sq.  mm.  (34-92  tons  per  sq.  in.) 
Elastic  Limit        =22  kg.  per  sq.  mm.  (13-97  tons  per  sq.  in.) 
%  Elongation      =24 
Shock  Resistance  =  6  kg.  m.  per  sq.  cm. 


80    Kg 

pen 


70 


§50 


LJ 


20 


mm1 


Tensile  Strength 


Elastic  Limit 


35 

M 

30  •- 

c. 

25     e'- 
en 

c 
200 

15 
10 
5 


100     200      300      400      500      600     700       800     900°C 
Annealing  Temperature 

FIG.  67. — Variation  in  Mechanical  Properties  (Tensile  and  Impact) 
with  Annealing  Temperature.  Forged  Aluminium  Bronze, 
Type  I  (Cu  90  %,  Al  10  %). 

(d)  VARIATION   IN   THE   MECHANICAL   PROPERTIES,   TENSILE 
AND  IMPACT,  WITH  QUENCHING  TEMPERATURE. 

(dj)  Alloy  as  Cast. 

The  variations  in  the  properties  are  summarised  in  Fig.  68. 

The  maximum  Shock  Resistance  and  Elongation  are  obtained 
by  quenching  from  600°,  which  results  in  the  following  proper- 
ties in  the  cast  metal : — 

Tensile  Strength  =56  kg.  per  sq.  mm.  (35-56  tons  per  sq.  in.) 
Elastic  Limit        =26  kg.  per  sq.  mm.  (16-51  tons  per  sq.  in.) 
%  Elongation      =12 
Shock  Resistance  =  6  kg.  m.  per  sq.  cm. 


—a  cUstinqt  improvement  on  the  original  cast  alloy. 


MECHANICAL  PROPERTIES 


125 


(d2)  Alloy  as  Forged. 

The  variations  in  the  properties  are  summarised  in  Fig.  69. 

Quenching  from  500°  has  little  effect  on  this  cupro-alu- 
minium,  which  retains  approximately  the  properties  that  it 
possessed  in  the  forged  state.  The  effect  of  quenching  from 
above  500°  is  distinctly  noticeable. 


so 


70 


60 


50 


c  40 
O 

U 


30 


20 


Kg 

per 
mm 


400 


500  600 

Quenching 


FIG.  68. — Variation  in  Mechanical  Properties  (Tensile  and 
Impact)  with  Quenching  Temperature.  Cast  Aluminium 
Bronze,  Type  I  (Cu  90  %,  Al  10  %). 

After  quenching  from  650° — 

Tensile  Strength  =64  kg.  per  sq.  mm.  (40-64  tons  per  sq.  in.) 

Elastic  Limit        =32  kg.  per  sq.  mm.  (20-32  tons  per  sq.  in.) 

%  Elongation      =16 

Shock  Resistance  =  8  kg.  m.  per  sq.  cm. 


126 


ALUMINIUM  AND  ITS  ALLOYS 


This  is  approximately  the  maximum  for  Shock  Resistance 
and  Elongation,  all  the  properties  being  superior  to  those 
of  the  quenched,  cast,  alloy. 

Quenched  from  above  650°,  the  Elongation  and  Shock  Re- 


400 


500  600  700  800 

Quenching    Temperature 


i50 


900°C 


FIG.  69. — Variation  in  Mechanical  Properties  (Tensile  and 
Impact)  with  Quenching  Temperature.  Forged  Aluminium 
Bronze,  Type  I  (Cu  90  %,  Al  10  %). 


sistance  decrease  while  the  Tensile  Strength  and  Elastic  Limit 
continue  to  increase,  so  that,  after  quenching  from  900°,  they 
have  the  following  values  : — 

Tensile  Strength  =  72  kg.  per  sq.  mm.  (45-72  tons  per  sq.  in.) 
Elastic  Limit       =44  kg.  per  sq.  mm.  (27*94  tons  per  sq.  in.) 


MECHANICAL  PROPERTIES 


127 


(e)  VARIATION  IN  THE  MECHANICAL  PROPERTIES,  TENSILE 
AND  IMPACT,  WITH  TEMPERATURE  OF  REANNEAL  SUB- 
SEQUENT TO  QUENCHING  THE  FORGED  ALLOY. 

The  following  quenching  temperatures  were  investigated  : — 

700° 
800° 
900° 

For  each  of  these,  investigation  was  made  as  to  the  effect 
of  reannealing  at  every  fifty  degrees  from  300°  to  a  temperature 
one  hundred  degrees  below  the  quenching  temperature. 


50 


45 


40 


35 


W 
J  40 

U 

'  o 


2C 


10 


Tensile  Strength 


Elastic  Limit 


10  Kg.  m 
per  cm* 


Elongation 


Shock 
Resistance 


100    200    300    400    500    600 

Annealing  Temperature 


so  «L 


25  & 

(0 

c 
20  £ 

15 
10 


7o8°C 


Fia.  70.— Variation  in  Mechanical  Properties  (Tensile  and  Impact) 
with  Temperature  of  Reanneal  after  Quenching  from  700°. 
Forged  Aluminium  Bronze,  Type  I  (Cu  90  %,  Al  10  %). 

(1)  Reanneal  after  Quenching  from  700°. 

The  results  are  summarised  in  Fig.  70. 
The  reanneal  which  produces  the  best  Tensile  Strength  and 
Elastic  Limit  is  one  at  300°,  giving  the  following  values  : — 


128 


ALUMINIUM  AND  ITS  ALLOYS 


Tensile  Strength  =80  kg.  per  sq.  mm.  (50-8  tons  per  sq.  in.) 
Elastic  Limit        =55  kg.  per  sq.  mm.  (34-92  tons  per  sq.  in.) 
%  Elongation      =  2 
Shock  Resistance  =  3  kg.  m.  per  sq.  cm. 

The  reanneal  which  produces  the  best  Elongation  and  Shock 
Resistance  is  one  at  600°,  when  the  values  are — 
Tensile  Strength  =58  kg.  per  sq.  mm.  (36-83  tons  per  sq.  in.) 
Elastic  Limit        =36  kg.  per  sq.  mm.  (22-86  tons  per  sq.  in.) 
%  Elongation      =20 
Shock  Resistance  =  5  kg.  m.  per  sq.  cm. 


100 


800 


200   300  400   500  600  700 

Annealing  Temperature 

FIG.  71. — Variation  in  Mechanical  Properties  (Tensile  and  Impact) 
with  Temperature  of  Reanneal  after  Quenching  from  800°.  Forged 
Aluminium  Bronze,  Type  I  (Cu  90  %,  Al  10  %). 

It  must  be  noted  that  the  first  reanneal  corresponds  with 
unsuitable  Elongation  and  too  great  brittleness,  and  the 
second  reanneal  has  no  advantage  over  simply  quenching  from 
700°,  when — 

Tensile  Strength  =66  kg.  per  sq.  mm.  (41-92  tons  per  sq.  in.) 
Elastic  Limit        =34  kg.  per  sq.  mm.  (21-59  tons  per  sq.  in.) 
%  Elongation      =18 
Shock  Resistance  =  7  kg.m.  per  sq.  cm. 


In  conclusion,  reannealing  after  quenching  from  700C 
the  alloy  no  valuable  properties. 


gives 


MECHANICAL  PROPERTIES 


129 


(2)  Reanneal  after  Quenching  from  800°. 

The  results  are  summarised  in  Fig.  71. 

The  reanneal  which   gives   the  best  Tensile  Strength  and 
Elastic  Limit  is  one  at  about  400°,  when  the  values  are  : — 

Tensile  Strength  =70  kg.  per  sq.  mm.  (44-45  tons  per  sq.  in.) 
Elastic  Limit        =50  kg.  per  sq.  mm.  (31-75  tons  per  sq.  in.) 
%  Elongation      =  2 
Shock  Resistance  =  1  kg.  m.  per  sq.  cm. 


200      300      400      500      600      700 
Annealing   Temperature 

FIG.  72. — Variation  in  Mechanical  Properties  (Tensile  and  Impact) 
with  Temperature  of  Reanneal  after  Quenching  from  900°. 
Forged  Aluminium  Bronze,  Type  I  (Cu  90  %,  Al  10  %). 

The  reanneal  which  produces  the  best  Elongation  and  Shock 
Resistance  is  one  at  about  600°,  when  the  values  are  : — 

Tensile  Strength  =60  kg.  per  sq.  mm.  (38-10  tons  per  sq.  in.) 
Elastic  Limit        =26  kg.  per  sq.  mm.  (16-51  tons  per  sq.  in.) 
%  Elongation      =22 
Shock  Resistance  =  8  kg.  m.  per  sq.  cm. 

Similar  remarks  apply  to  these  two  reanneals  as  in  the 
preceding  case. 

(3)  Reanneal  after  Quenching  from  900°. 

The  results  are  summarised  in  Fig.  72. 

The  reanneal  which  gives  the  best  Tensile  Strength  and 
Elastic  Limit  is  one  at  about  300°,  when  the  values  are : — 


130  ALUMINIUM  AND  ITS  ALLOYS 

Tensile  Strength  =75  kg.  per  sq.  mm.  (47-62  tons  per  sq.  in.) 
Elastic  Limit        =48  kg.  per  sq.  mm.  (30-48  tons  per  sq.  in.) 
%  Elongation      =0-5 
Shock  Resistance  =  3  kg.  m.  per  sq.  cm. 

The  reanneal  which  gives  the  best  Elongation  and  Shock 
Resistance  is  one  at  about  600°,  when  the  values  are  : — 

Tensile  Strength  =58  kg.  per  sq.  mm.  (36-83  tons  per  sq.  in.) 
Elastic  Limit        =28  kg.  per  sq.  mm.  (17-78  tons  per  sq.  in.) 
%  Elongation      =34 
Shock  Resistance  =  12  kg.  m.  per  sq.  cm. 

The  first  reanneal  is  of  no  value  on  account  of  the  great 
brittleness  that  it  causes.  On  the  contrary,  the  second  reanneal 
is  of  the  greatest  importance  since  it  produces  in  aluminium 
bronze  most  remarkable  properties,  namely  : — 

(a)  Elongations  comparable  with,  or  even  superior  to,  those 

of  the  softest  steels  or  of  high  nickel  steels  (more  than 
30  %  nickel). 

(b)  A  sufficiently  large  Shock  Resistance. 

(c)  Tensile  Strengths  comparable  with  those  of  tempered 

steels. 

CONCLUSION. 

The  following  is  the  optimum  thermal  treatment  for  cupro- 
aluminium  (Type  I)  (90  %  copper,  10  %  aluminium)  :— 

Quenching  from  900°. 
Reannealing  at  675°-700°. 

(/)  HARDNESS  AT  HIGH  TEMPERATURES. 

Hardness  tests  at  high  temperatures  were  carried  out  on 
cylinders,  2  cm.  in  diameter,  and  2  cm.  high,  as  in  the  case  of 
the  light  alloys  of  great  strength. 

A  ball,  10  mm.  in  diameter,  was  used  under  a  load  of  500  kg., 
and  the  tests  were  made  at  every  fifty  degrees  from  the  normal 
temperature  up  to  800°. 

The  hardness  at  high  temperatures  of  cupro-aluminium, 
Type  I,  was  investigated  under  three  conditions  : — 

(1)  Alloy  as  forged  (worked). 

(2)  Alloy  as  cast. 

(3)  Alloy  quenched  from  900°  and  reannealed  at  700°. 


MECHANICAL  PROPERTIES 


131 


The  results  of  the  tests  are  summarised  in  Fig.  726,  and 
may  be  stated  as  follows  : — 

Normal  Temperature. 

Hardness  of  worked  alloy  under  500  kg.  =  1 50-1 60 

Hardness  of  cast  alloy  under  500  kg.  =  100-1 10 

Hardness  of  quenched  and  reannealed  alloy  under 

500  kg.  =  110-120 


and  fteannealed  \Worked 
\ 


100       200 


300       400       500 

Temperature 


600       700       800  °C 


FIG.  726. — High-temperature  Hardness  Tests  (500  Kg.)  on 
Aluminium  Bronze,  Type  I : — 

auenched  from  900°.  reannealed  at  700°. 

after  work  (forging — pressing). 


—  —  —  —  —  —  —    as  cast. 


Effect  of  Temperature. 

The  alloy,  Type  I,  possesses  in  all  three  states  a  minimum 
hardness  over  the  range  of  temperature  100-200°. 

The  worked  alloy  retains  a  greater  hardness  at  all  tempera- 
tures. 

The  cast  alloy,  although  less  hard  than  the  other  two,  has, 
still,  at  high  temperatures,  an  appreciable  value.  (Compare 
results  with  those  of  the  casting  alloys.) 

The  heat-treated  alloy  possesses  at  all  temperatures  a 
hardness  lying  between  the  two  preceding. 


132 


ALUMINIUM  AND  ITS  ALLOYS 


II.    TYPE  II 

Cupro- Aluminiums  containing  89  %  Copper,  10  %  Alu 

minium,  1  %  Manganese 
(a)  CHEMICAL  ANALYSIS. 

Copper       .          .          .          .89 
Aluminium          .          .          .9-50 
Manganese  .          .          .       0-95 

Iron  .          .       0-25 

Nickel        .          .          .          .nil 
Lead          .          .          .          .nil 

Tin nil 

Difference  .          .          .       0-30 

100-00 


FIG.  73. — Aluminium  Bronze,  Type  II. 


10"' 


FIG.  74. — Aluminium  Bronze,  Type  II. 

(b)  INVESTIGATION  OF  CRITICAL  POINTS. 
Cupro-aluminium,  Type  II,  undergoes  a  single  transformation 

on  heating,  as  also  on  cooling  (see  Figs.  73  and  74). 

(c)  VARIATION    IN    TJHE    MECHANICAL   PROPERTIES,    TENSILE 

AND  IMPACT,  WITH  THE  ANNEALING  TEMPERATURE, 
or  THE  FORGED  ALLOY,  TYPE  II. 

The  results  of  the  tests  are  summarised  in  Fig.  75,  which 
shows  that  a  single  anneal  is  of  no  value,  the  alloy  in  the  forged 
state  possessing  the  following  properties  : — 

Tensile  Strength  =55  kg.  per  sq.  mm.  (34-92  tons  per  sq.  in.) 
Elastic  Limit        =24  kg.  per  sq.  mm.  (15-24  tons  per  sq.  in.) 
%  Elongation      =  3-5 
Shock  Resistance  =  4-5  kg.  m.  per  sq.  cm. 


MECHANICAL  PROPERTIES 


133 


(d)  VARIATION  IN  THE  MECHANICAL  PROPERTIES,  TENSILE 
AND  IMPACT,  WITH  THE  QUENCHING  TEMPERATURE, 
FORGED  ALLOY,  TYPE  II. 

The  results  of  the  tests  are  summarised  in  Fig.  76. 

It  is  only  after  the  transformation  point  has  been  passed, 
i.e.  between  500°  and  600°,  that  the  effect  of  the  quenching 
becomes  visible. 


'0         TOO      200      300      400      500      600      700      800      900  °C 
Annealing    Temperature 

FIG.  75. — Variation  in  Mechanical  Properties  (Tensile  and  Impact) 
with  Annealing  Temperature.  Forged  Aluminium  Bronze, 
Type  II  (Cu  89  %,  Mn  1  %,  Al  10  %). 

The  maximum  properties  after  quenching,  not  followed  by 
a  reanneal,  are  produced  by  quenching  from  700°,  when  these 
values  are  as  follows  : — 

Tensile  Strength  =55  kg.  per  sq.  mm.  (34-92  tons  per  sq.  in.) 
Elastic  Limit        =24  kg.  per  sq.  mm.  (15-24  tons  per  sq.  in.) 
%  Elongation      =35 
Shock  Resistance  =  12  kg.  m.  per  sq.  cm. 

This  treatment  without  reanneal  is,  therefore,  of  value  only 
as  regards  Shock  Resistance  for  alloys  of  Type  II,  the  Shock 
Resistance  being  12  kg.  m.  per  sq.  cm.  instead  of  4-5,  as  in  the 
forged  state,  but  the  other  properties  remain  approximately 
the  same. 


134 


ALUMINIUM  AND  ITS  ALLOYS 


(e)  VARIATION  IN  THE  MECHANICAL  PROPERTIES,  TENSILE  AND 
IMPACT,  WITH  TEMPERATURE  OF  REANNEAL,  SUBSE- 
QUENT TO  QUENCHING  THE  FORGED  ALLOY,  TYPE  II. 

The  following  quenching  temperatures  were  studied  :  800° 
and  900°. 

The  reanneals  were  carried  out  under  the  same  conditions 
as  in  the  case  of  Type  I. 


80 


70 


60 


§50 

L 

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Ld 
$30 


20 


10 


Kg.  per 


mm/ 


%£/on 


12  $> 
a 

10   £ 


ests  t 


50 
45 
40 
35 

30  °c 

c. 
25    « 

o» 

20    § 

H 
15 

Z/7C0 
10 


400     500      600     700      800      900°C 
Quenching  Temperature 

FIG.  76. — Variation  in  Mechanical  Properties  (Tensile  and  Impact) 
with  Quenching  Temperature.  Forged  Aluminium  Bronze, 
Type  II  (Cu  89  %,  Mn  1  %,  Al  10  %). 

(1)  Reanneal  after  Quenching  from  800°. 
The  results  are  summarised  in  Fig.  77. 

The  anneal  which  produces  the  best  Tensile  Strength  and 
Elastic  Limit  is  one  at  about  400°,  when  the  values  are  : — 
Tensile  Strength  =70  kg.  per  sq.  mm.  (44-45  tons  per  sq.  in.) 
Elastic  Limit        —28  kg.  per  sq.  mm.  (17-78  tons  per  sq.  in.) 
%  Elongation      =14 
Shock  Resistance  =  3  kg.  m.  per  sq.  cm. 

On  the  other  hand,  the  anneal  producing  the  best  Elongation 
and  Shock  Resistance  is  one  at  750°,  when  the  values  are  : — 
Tensile  Strength  =  54  kg.  per  sq.  mm.  (34-29  tons  per  sq.  in.) 
Elastic  Limit        =22  kg.  per  sq.  mm.  (13-97  tons  per  sq.  in.) 
%  Elongation     =38 
Shock  Resistance=14  kg.  m.  per  sq.  cm. 


MECHANICAL  PROPERTIES 


135 


100  200  300   400   500   600   700   800   900°C 

Annealing  Temperature 

FIG.  77. — Variation  in  Mechanical  Properties  (Tensile  and  Impact) 
with  Temperature  of  Reanneal  after  Quenching  from  800°. 
Forged  Aluminium  Bronze,  Type  II  (Cu  89  %,  Mn  1  %,  Al  10%). 


80y 


100      200      300     400      500      600      700      800      900 °C 
Annealing  Temperature 

Fio.  78. — Variation  in  Mechanical  Properties  (Tensile  and  Impact) 
with  Temperature  of  Reanneal  after  Quenching  from  900°.  Forged 
Aluminium  Bronze,  Type  II  (Cu  89  %,  Mn  1  %,  Al  10  %). 


136 


ALUMINIUM  AND  ITS  ALLOYS 


(2)  Reanneal  after  Quenching  from  900°. 

The  results  are  summarised  in  Fig.  78. 

The  best  Tensile  Strength  and  Elastic  Limit  are  produced 
by  an  anneal  at  about  350°,  which  does  not  cause  any  important 
changes  in  the  alloy. 


100       200 


300       400       500 
Temperature 


600       700       800  °C 


FIG.  786. — High-temperature  Hardness  Tests  (500  Kg.)  on  Aluminium 
Bronze,  Type  II,  Quenched  from  900°,  Reannealed  at  600°. 

The  best  Elongation  and  Shock  Resistance  are  produced  by 
an  anneal  at  about  750°,  when  the  values  are  : — 

Tensile  Strength  =  54  kg.  per  sq.  mm.  (34-29  tons  per  sq.  in.) 
Elastic  Limit        =20  kg.  per  sq.  mm.  (12-7  tons  per  sq.  in.) 
%  Elongation     =45 
Shock  Resistance=14  kg.  m.  per  sq.  cm. 

This  cupro-aluminium,  containing  1  %  manganese,  acquires, 
as  a  result  of  this  treatment,  very  remarkable  properties. 

The  Tensile  Strength  and  Elastic  Limit,  approaching  those 
of  the  tempered  steels,  are  surpassed  in  importance  by  the 
great  Elongation  and  unusual  Shock  Resistance. 

CONCLUSION. 

The  optimum  thermal  treatment  for  cupro-aluminium  con- 
taining 1  %  of  manganese,  i.e.  Type  II,  is  as  follows  :  quenching 
from  900°,  followed  by  reannealing  at  750°. 


MECHANICAL  PROPERTIES  137 

(/)  HARDNESS  AT  HIGH  TEMPERATURES. 

The  hardness  tests  at  high  temperatures  were  carried  out 
under  the  same  conditions  as  for  Type  I,  and  the  results  are 
shown  in  Fig.  786. 

They  were  carried  out  only  on  the  heat-treated  alloy 
(quenched  from  900°  and  reannealed  at  600°). 

They  reveal  a  greater  hardness  than  that  of  Type  I  for  all 
temperatures  between  0°  and  500°,  but  a  slightly  lower  hard- 
ness for  temperatures  above  500°. 

010     100       200       300       400       500       600       7QO    . 


FIQ,  79. — Aluminium  Bronze,  Type  III  (Dilatometer). 


III.    TYPE  in 


81  %  Copper,  11  %  Aluminium,  4  %  Nickel, 
4  %  Iron 


(a)  CHEMICAL  ANALYSIS. 

Copper 

Aluminium 

Manganese 

Iron 

Nickel 

Lead 

Tin  . 

Difference 


80-95 
10-60 
0-45 
4-40 
3-55 
nil 
nil 
0-05 

100-00 


(6)  INVESTIGATION  OF  THE  CRITICAL  POINTS. 

Neither  the  expansion  curve  nor  the  curve  of  temperature 
plotted  against  time  indicates  the  slightest  transformation 
(see  Figs.  79  and  80). 


138 


ALUMINIUM  AND  ITS  ALLOYS 


,*ui 


SUOJL 


s. 

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o    +J 

O       (tf 

CO        SL 


O      e      C  °D 

s  I  £03 

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M 


MECHANICAL  PROPERTIES 


139 


(c)  VAKIATION  IN  THE  MECHANICAL  PROPERTIES,  TENSILE 
AND  IMPACT,  WITH  THE  ANNEALING  TEMPERATURE, 
FOR  THE  FORGED  ALLOY,  TYPE  III. 

The  results  of  the  tests  are  summarised  in  Fig.  81,  which 
shows  that  this  cupro-aluminium  in  the  forged  state  possesses 
the  following  properties  : — 

Tensile  Strength  =76  kg.  per  sq.  mm.  (48-26  tons  per  sq.  in.) 

Elastic  Limit        =56  kg.  per  sq.  mm.  (35-56  tons  per  sq.  in.) 

%  Elongation     =12 

Shock  Resistance=  2  kg.  m.  per  sq.  cm. 


80T 


70 


60 


50 


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UJ 


30 


20 


10 


Kg 
per 


Tensile  Strength 


Elastic  Limit 


50 


45 


40 


35 


30 


per 
cm* 


%  Elongation 


25 


20 


'400          500  600  700  800 

Quenching  Temperature 


908*0 


FIG.  82. — Variation  in  Mechanical  Properties  (Tensile  and  Impact) 
with  Quenching  Temperature.  Forged  Aluminium  Bronze,  Type 
UI  (Cu  81  o/o,  Ni  4  %,  Fe  4  %,  Al  11  %). 


140 


ALUMINIUM  AND  ITS  ALLOYS 


Annealing  seems  to  have  no  effect  up  to  400-500°.  Above 
500°,  annealing  has  the  effect  of  diminishing  the  Elastic  Limit 
and  of  improving  the  Elongation  and  Shock  Resistance,  whilst 
the  Tensile  Strength  remains  unchanged. 

Thus,  after  annealing  at  900°,  the  alloy  has  the  following 
properties  : — 

Tensile  Strength  =75  kg.  per  sq.  mm.  (47-62  tons  per  sq.  in.) 
Elastic  Limit        =36  kg.  per  sq.  mm.  (22-86  tons  per  sq.  in.) 
%  Elongation      =26 
Shock  Resistance  =  4  kg.  m.  per  sq.  cm. 


100   200   300  400   500   600   700   800  900°C 

Annealing   Temperature 

FIG.  83. — Variation  in  Mechanical  Properties  (Tensile  and 
Impact)  with  Temperature  of  Reanneal  after  Quenching 
from  900°.  Forged  Aluminium  Bronze,  Type  III  (Cu  81  %, 
Ni  4  %,  Fe  4  %,  Alll  %). 


(d)  VARIATION  IN  THE  MECHANICAL  PROPERTIES,  TENSILE 
AND  IMPACT,  WITH  THE  QUENCHING  TEMPERATURE 
FOR  THE  FORGED  ALLOY,  TYPE  III. 

The  results  of  the  tests  are  shown  in  Pig.  82,  which  shows 
that  the  change  in  the  properties  of  the  alloy  after  quenching 
is  only  insignificant. 


MECHANICAL  PROPERTIES 


141 


(e)  VARIATION    IN   THE   MECHANICAL   PROPERTIES,    TENSILE 

AND  IMPACT,  WITH  THE  TEMPERATURE  OF  REANNEAL, 

SUBSEQUENT   TO   QUENCHING   THE   FORGED    ALLOY, 

TYPE  III. 

The  results  of  reannealing  after  quenching  from  900°  are 

shown  in  Fig.  83,  which  shows  that  the  mechanical  properties 

undergo  no  appreciable  improvement  after  quenching  from 

900°  and  reannealing. 

CONCLUSION. 

The  following  method  of  working  seems  to  be  advisable : 
annealing  at  900°,  followed  by  cooling  in  air. 

(/)  HARDNESS  AT  HIGH  TEMPERATURES. 

The  results  are  summarised  in  Fig.  836. 

The  tests  were  carried  out  on  metal  annealed  at  900°,  and 
show,  for  all  temperatures,  a  hardness  greater  than  that  of 
the  alloys  of  Types  I  and  EL 

180 
170 
160 
150 
140 
130 
120 

o  no 

£  100 
Z  90 
^  80 
|  70 

50 
40 
30 
20 
10 


0    100   200   300   400   500   600   700   800 

Temperature 

FIG.  836.— High-temperature  Hardness  Tests  (500  Kg.)  on 
Aluminium  Bronze,  Type  III,  Annealed  at  900°. 


CHAPTER  III 
MICROGRAPHY 

As  we  have  seen,  the  alloys  studied  contain  from  88  %  to  92  % 
of  copper,  and  in  that  range  consist  of  the  solid  solution  a 
plus  the  eutectoid  (a -f  y).  At  88  %  of  copper,  the  alloy  consists 
of  almost  pure  eutectoid,  below  that  value  the  y  constituent 
makes  its  appearance.  We  have,  therefore,  only  to  consider 
the  hypoeutectoid  alloys,  and  to  study  the  solution  a  and  the 
eutectoid  (a-f  y). 

EXPERIMENTAL  DETAILS. 

Shock  test  pieces,  which  had  received  varying  treatment, 
were  used  for  micrographic  examination. 

Robin's  reagent  was  used  for  etching.    This  consists  of*: — 

Ferric  chloride    .  .  5  % 

Water        .          .  .  5  % 

Hydrochloric  acid  .  .     30  % 

Isoamyl  alcohol  .  30  % 

Ethyl  alcohol      .  .  .30  % 

The  following  is  the  most  general  and  complete  scheme  of 
investigation  for  a  typical  alloy  : — 

Micrographic  examination  of  sections  of 

(a)  Metal  annealed  after  forging  or  casting. 

(6)  Metal  quenched  from  different  temperatures. 

(c)  Metal  quenched  and  reannealed  at  different  temperatures. 

(d)  Cast  or  worked  metal. 


I.    CUPRO- ALUMINIUM,  TYPE  I 

(a)  MICROGRAPHIC  EXAMINATION  OF  SECTIONS  OF  METAL 
FORGED  AND  SUBSEQUENTLY  ANNEALED  AT  DIFFERENT 
TEMPERATURES. 

Plates  I  and  II  give  the  microphotographs  of  these  sections. 
We  will  comment  upon  them  in  turn. 

142 


PLATE   I. 
TYPE   I.     FORGED  AND  ANNEALED. 


PHOTOGKAPH  1. 

CUPRO-ALUMINIUM.       As    FORGED. 

X60. 


PHOTOGRAPH  '2. 

CUPRO-ALUMINIUM.     As  FORGED. 
X  225. 


PHOTOGRAPH  3. 

CUPRO-ALUMINIUM.     FORGED  AND 
SUBSEQUENTLY  ANNEALED  AT  300°. 

X60. 


PHOTOGRAPH  4. 
CUPRO-ALUMINIUM.     FORGED  AND 

SUBSEQUENTLY    ANNEALED    AT    300°. 

X  225. 


To  face  page  143 


PLATE  IB. 
:  'TYPE  I.  EUTECTIC  STRUCTURE. 


PHOTOGRAPH  A. 

EUTECTIC  STRUCTURE.     ETCHED   WITH 
ALCOHOLIC  FERRIC  CHLORIDE. 

X  500. 
(Portevin.) 


PHOTOGRAPH  B. 

EUTECTIC  STRUCTURE.     ETCHED  WITH 
ALCOHOLIC  FERRIC  CHLORIDE. 

X870. 
(Portevin.) 


PHOTOGRAPH  C. 

SHOWING  TWO  EUTECTIC  FORMATIONS — 

CELLULAR  AND  LAMELLAR. 

'A  500. 


PHOTOGRAPH  D. 
HYPEREUTECTOID  ALLOY. 
EUTECTIC   +7. 
X200. 


ETCHED  WITH  ALCOHOLIC  FERRIC  CHLORIDE.       ETCHED  WITH  ALCOHOLIC  FERRIC  CHLORIDE. 


(Portevin.) 


(Portevin.) 

To  faeo  page  143 


PLATE  II. 
TYPE   I.     FORGED  AXD   SUBSEQUENTLY  ANNEALED. 


PHOTOGRAPH  5. 

CUPRO-ALUMINIUM.     FORGED  AND 
SUBSEQUENTLY  ANNEALED  AT  700°. 

x60. 


PHOTOGRAPH  6. 

CUPRO- ALUMINIUM.     FORGED  AND 
SUBSEQUENTLY  ANNEALED  AT  700°. 

X225. 


PHOTOGRAPH  7. 

CUPRO-ALUMINIUM.     FORGED  AND 
SUBSEQUENTLY  ANNEALED  AT  900°. 

X60. 


PHOTOGRAPH  8. 

CUPRO-ALUMINIUM.     FORGED  AND 
SUBSEQUENTLY  ANNEALED  AT  900°. 

X225. 


To  face  page  143. 


PLATE  III. 
AND  SUBSEQUENTLY  QUENCHED. 


PHOTOGRAPH  9. 

CUPBO -ALUMINIUM.       FORGED    AND 
SUBSEQUENTLY    QUENCHED    FROM    500C 

X60. 


PHOTOGRAPH  10 
CUPRO- ALUMINIUM.     FORGED  AND 

SUBSEQUENTLY    QUENCHED    FROM    500°. 

X225. 


PHOTOGRAPH  11. 

CUPRO-ALUMINIUM.      FORGED    AND 
SUBSEQUENTLY    QUENCHED    FROM    600°. 

X60. 


PHOTOGRAPH  12. 

CUPRO-ALUMINIUM.     FORGED  AND 
SUBSEQUENTLY  QUENCHED  FROM  600C 

X225. 


To  face  page  143. 


PLATE   IY. 
TYPE   I.     FORGED  AND   SUBSEQUENTLY   QUENCHED. 


PHOTOGRAPH  13. 

CUPRO- ALUMINIUM.       FORGED    AND 
SUBSEQUENTLY    QUENCHED    FROM    700C 

X60. 
(Breuil.) 


PHOTOGRAPH  14. 
CUPRO-ALUMINIUM.     FORGED  AND 

SUBSEQUENTLY    QUENCHED    FROM    700C 

X225. 
(Breuil.) 


PHOTOGRAPH  15. 

CUPRO-ALUMINIUM.     FORGED  AND 
SUBSEQUENTLY  QUENCHED  FROM  800°. 

x60. 
(Breuil.) 


PHOTOGRAPH  16. 
CUPRO-ALUMINIUM.     FORGED  AND 

SUBSEQUENTLY    QUENCHED    FROM    800°. 

x225. 
(BreuiL) 


To  face  page  143 


PLATE  V. 
TYPE  I.     FORGED  AND   SUBSEQUENTLY   QUENCHED. 


PHOTOGRAPH  17. 
CUPRO-ALUMINIUM.    FORGED  AND 

SUBSEQUENTLY    QUENCHED    FROM    900°. 

x60. 
(Breuil.) 


PHOTOGRAPH  18. 
CUPRO-ALUMINIUM.    FORGED  AND 

SUBSEQUENTLY    QUENCHED    FROM    900°. 

X225. 
(Breuil.) 


To  face  pa^e  143. 


MICROGRAPHY  /'-  /,  : 

(i)  Forged  Alloy  (not  subsequently  annealed). 

See  Photographs  1  and  2  of  Plate  I. 

We  note  the  two  constituents  previously  mentioned — the 
a  constituent  and  the  (a-J-y)  eutectoid,  which  we  will  call 
E.  The  a  constituent  appears  as  white  dendrites,  while  the 
eutectoid  appears  black. 

According  to  Porte vin,*  the  constitution  of  the  eutectoid 
is  as  follows  : — 

"  The  f$  constituent  f  of  the  aluminium  bronzes  can  exhibit 
two  formations,  firstly,  a  cellular  or  honeycombed  network  ; 
and,  secondly,  a  considerably  finer,  lamellar,  structure,  analo- 
gous to  the  pearlite  in  annealed  steels. 

These  two  formations  can  coexist  in  contiguous  portions  of 
the  same  alloy,  the  reticular  form  being  favoured  in  the  portions 
adjacent  to  the  proeutectoid  constituent  a. 

The  lamellar  form  of  eutectic  is  only  capable  of  resolution 
under  high  magnifications  in  slowly  cooled  alloys,  while, 
under  the  same  conditions  of  cooling,  the  reticular  form  is 
visible  under  low  magnifications." 

See  Portevin's  microphotographs,  Plate  IB. 

(ii)  Effect  of  Annealing  after  Forging. 

See  Photographs  3-8  inclusive,  Plates  I  and  II. 

Whatever  the  temperature  of  anneal  after  forging,  the  con- 
stituent a  and  the  eutectoid  E  are  seen  to  be  present.  Annealing 
leads  to  a  certain  amount  of  separation  of  the  dendrites  of  the 
a  constituent ;  the  needles  arrange  themselves  in  parallel 
lines,  and  the  intersections  of  the  various  groups  give  rise  to 
polyhedric  outlines,  forming,  as  it  were,  the  crystal  boundaries. 
These  outlines  increase  in  size  as  the  temperature  rises — a  high 
temperature  anneal  practically  gives  rise  to  exaggerated  grain 
size.  This,  however,  does  not  involve  a  lowering  of  the  percen- 
tage Elongation  or  of  the  Shock  Resistance,  as  occurs  in  steel 
and  certain  alloys. 

Breuil  explains  this  phenomenon  on  the  assumption  that 
crystals  possessing  a  given  orientation  are  united  to  those  in 
an  adjacent  zone  by  means  of  connecting  filaments,  without 
there  being  any  abrupt  break,  as  in  certain  other  metals. 

*  Portevin,  "Internationale  Zeitschrift  fur  Metallographie,"  X,  948, 
1913. 

t  The  author  refers  to  the  (a  +  -y)  eutectoid  as  /3.  We  call  this  E.  The 
term  "  /S  "  should  be  retained,  as  curry's  diagram  shows,  for  the  constituent 
analogous  to  the  austenite  in  steels. 


ALUMINIUM  AND  ITS  ALLOYS 


(b)  MICKOGRAPHIC    EXAMINATION    OF    SECTIONS    QUENCHED 

AND    NOT   SUBSEQUENTLY   ANNEALED. 

The  diagrams  relating  to  critical  points  revealed  the  fact 
that  all  these  points  only  make  their  appearance  if  the  tempera- 
ture exceeds  500°. 

The  highest  point,  Ac3,  plays  an  essential  part,  and  must 
be  passed,  on  heating,  if  structural  modifications  are  to  be 
expected  on  cooling. 

Actually,  Ac3  appears  at  about  570°,  and  Arl5  on  cooling, 
occurs  at  520°.  It  is,  therefore,  only  above  600°  that  the 
effect  of  quenching  becomes  appreciable. 

Generally  speaking,  quenched  alloys  exhibit  a  martensitic, 
acicular  structure,  possessing  a  triangular  arrangement.  The 
structure  varies  with  the  quenching  conditions,  thus  showing 
a  very  great  similarity  to  the  martensite  of  steels. 

The  a  constituent  seems  gradually  to  disappear  as  the 
quenching  temperature  rises.  It  seems  to  be  reabsorbed  or 
to  dissolve  in  the  eutectoid  E  in  the  form  of  fine  white  needles. 
This  solution  we  shall  call  M,  in  order  not  to  employ  the  letter 
y,  often  used,  but  which,  in  Curry's  diagram,  has  a  different 
significance. 

Looking  at  the  microphotographs  9-18  inclusive,  Plates 
III,  IV,  and  V,*  we  observe  the  progressive  disappearance  of 
the  separate  constituent.  It  is  present  after  quenching  from 
500°,  slightly  lessened  in  amount  after  quenching  from  600°, 
extremely  diminished  in  amount  after  quenching  from  700°, 
and  has  almost  completely  disappeared  after  quenching  from 
800°. 

For  quenching  to  be  complete,  therefore,  the  temperature 
must  rise  considerably  above  the  critical  point,  which  occurs 
at  570°,  and  at  which  the  transformation  commences. 

We  may  presume  that  an  increase  in  the  times  of  anneal 
would  have  the  same  effect  as  a  rise  in  temperature,  i.e.  that 
a  very  prolonged  anneal  at  750°  would  give  the  same  results 
as  an  anneal  of  much  shorter  duration  at  850°. 

However  that  may  be,  for  normal  and  industrial  annealing 
times,  it  is  necessary  that  the  temperature  should  exceed  800°, 
for  the  solution  M  to  extend  throughout  the  whole  mass  of 
metal.  It  can  only  be  decided  whether  800°  or  900°  should 
be  employed  after  studying  the  effects  of  reannealing. 

*  Photographs  13-18,  inclusive,  are  taken  from  a  research  by  Breuil  on 
this  particular  alloy  (known  as  mangalum,  No.  100,  Societe  des  Bronzes 
forgeables,  31st  May,  1918). 


PLATE  VI. 
TYPE   I.     FORGED,    QUENCHED,   AXD   REANNEALED. 


PHOTOGRAPH  19. 

CUPRO-ALUMINIUM.       FORGED,     QUENCHED 
FROM    900°,    REAXXEALED    AT    300°. 

x60. 


PHOTOGRAPH  20. 
CUPRO-ALUMIXIUM.    FORGED,  QUENCHED 

FROM    900°,    REAXXEALED    AT    300°. 

X225. 


PHOTOGRAPH  21. 
CUPRO-AXUMIXIUM.    FORGED,  QUEXCHED 

FROM    900°,    REAXXEALED    AT    600°. 

X60. 


PHOTOGRAPH  22. 
CL*PRO-AXUMIXIUM.    FORGED,  QUENCHED 

FROM    900°,    REAXXEALED    AT    600°. 

X225. 


To  face  page  144. 


PLATE  VIII.  / 

TYPE   I.     CAST  AND  ANXEALED. 


PHOTOGRAPH  27. 

CUPRO-ALUMINIUM.     A.S  CAST. 

X60. 


PHOTOGRAPH  28. 

CUPRO-ALUMINIUM.        As    CAST. 

X225. 


PHOTOGRAPH  29. 

CUPRO-ALUMINIUM.     CAST  AND 

ANNEALED  AT  800°. 

X60. 


PHOTOGRAPH  30. 

CUPRO-ALUMINIUM.     CAST  AND 

ANNEALED  AT  800°. 

X225. 


To  face  page  144 


PLATE   IX. 
TYPE   I.     CAST  AND  ANNEALED. 


PHOTOGRAPH  31. 

CUPRO-ALTJMINITJM.     CAST  AND 

ANNEALED  AT  900°. 

X60. 


PHOTOGRAPH  32. 

CUPRO-ALTJMINIUM.       CAST    AND 

ANNEALED    AT    900°. 

X225. 


To  face  page  144. 


PLATE   X. 
TYPE   I.     CAST  AND  QUENCHED. 


PHOTOGRAPH  33. 

CtJPRO- ALUMINIUM.     CAST  AND 

QUENCHED  FROM  500°. 

X60. 


PHOTOGRAPH  34. 

CUPRO-ALUMINIUM.     CAST  AND 

QUENCHED  FROM  600°. 

X60. 


PHOTOGRAPH  35. 

CUPRO-ALUMINIUM.     CAST  AND 

QUENCHED  FROM  700°. 

X60. 


To  face  page  144. 


PLATE   X.—  continued. 
TYPE   I.     CAST  AND  QUENCHED'.' 


PHOTOGRAPH  36. 

CUPRO- ALUMINIUM.     CAST  AND 

QUENCHED  FROM  800°. 

X60. 


PHOTOGRAPH  37. 
CUPRO- ALUMINIUM.     CAST  AND 

QUENCHED    FROM    900°. 

X60. 


To  face  page  144. 


PLATE   XI. 
TYPE   II.     FORGED  AND  ANNEALED 

'*S<26WV 


•ft-!    V"'    ir*-<    Jj'<  S  "  ";T>VAV»JV/ r-'-vT".'-     W^>su. 

iM' 

!l^??^^^^7?S^K^J^ 


PHOTOGRAPH  38. 

CUPRO-ALUMINIUM.     A3  FORGED. 

X60. 


PHOTOGRAPH  39. 
CUPRO-ALUMINIUM.     As  FORGED. 

X225. 


PHOTOGRAPH  40. 
CUPBO-AUTMXNIUH.      FORGED  AND 

SUBSEQUENTLY    ANNEALED    AT    800°. 
X60. 


PHOTOGRAPH  41. 

CUPRO-ALUMINIUM.    FORGED  AND 
SUBSEQUENTLY  ANNEALED  AT  800° 
X225. 


To  face  page  1-44 


PLATE  XII. 
TYPE   II.     QUENCHED  AND   REANNEALED. 


PHOTOGRAPH  42. 

CUPRO-ALTJMINITJM.     QlJEXCHED  FROM  900° 
REAXNEALED  AT  600°. 

X60. 


rv^r          v  ^ 

\,f<  ^?T     ^>-.^i/^V_.  ^, •     fe-^    '         •     ,  .^^ 


PHOTOGRAPH  43. 

CUPRO-ALUMINIUM.     QUENCHED  FROM  900°, 

REA3JNEALED  AT  600°. 

X  225. 


To  face  page  144 


PLATE   XIII. 
TYPE   III.     FORGED  AND  ANNEALED. 


PHOTOGRAPH  44. 

CUPRO- ALUMINIUM.       As    FORGED. 

X60. 


PHOTOGRAPH  45. 

CUPRO- ALUMINIUM.   As  FORGED. 

X225. 


PHOTOGRAPH  46. 
CUPRO -ALUMINIUM.    FORGED  AND 

ANNEALED    AT    600°. 
X60. 


PHOTOGRAPH  47. 
CUPRO-ALUMINIUM.      FORGED  AND 

ANNEALED    AT    600°. 
X225. 


To  face  page  144. 


PLATE  XIV. 
TYPE  III.     FORGED   AND  ANNEALED. 


PHOTOGRAPH  48. 

CUPRO-ALUMINIUM.    FORGED  AND 

ANNEALED  AT  800°. 

x60. 


PHOTOGRAPH  49. 
CUPRO-ALUMINIUM.    FORGED  AND 

ANNEALED    AT    900°. 

x225. 


TV.  faon  r.a™   111 


PLATE  XV.  "".•J-'V:* 

TYPE  III.     FORGED   AXD   QUENCHED. 


PHOTOGRAPH  50. 

CUPRO- ALUMINIUM.     QUENCHED  FROM  500°. 
X60. 


PHOTOGRAPH  51. 
CUPRO- ALUMINIUM.     QUENCHED  FROM  50( 

X225. 


PHOTOGRAPH  52. 

CL-PRO- ALUMINIUM.     QUENCHED  FROM  800°. 
X60. 


PHOTOGRAPH  53. 

CUPRO -ALUMINIUM.      QUENCHED    FROM    8(K 

X225. 


To  face  page  144. 


PLATE  XVI.  **-    , 

TYPE  III.    FORGED  AND  QUENCHED. 


PHOTOGRAPH  54. 

CUPRO-ALUMINITJM.      QUENCHED    FROM    900C 

X60. 


PHOTOGRAPH  55. 

CUPRO-ALUMINIUM.     QUENCHED  FROM  900°. 
X225. 


To  face  page  144. 


PLATE   XVII. 
TYPE   III.     QUENCHED   AND   REANXEALED." 


PHOTOGRAPH  56. 

CCPRO-ALUMINIUM.       QUENCHED    FROM    900' 
REANNEALED    AT    500°. 

X60. 


PHOTOGRAPH  57. 

CIJPRO- ALUMINIUM.     QUENCHED  FROM  900°, 
REANNEALED  AT  500°. 

X225. 


PHOTOGRAPH  58.  PHOTOGRAPH  59. 

CPRO-AO-.MINirM.       Q(   EXCHED    FROM    900°,  CUPRO-ALUMINIUM.       QUENCHED    FROM    900° 
REANNEALED    AT    600°.  REANNEALED    AT    600° 

«i<i.  x225. 


To  face  page  144. 


MICROGRAPHY  145 

(c)  MlCROGRAPHIC     EXAMINATION     OF     SECTIONS     QUENCHED 

AND    RE  ANNEALED. 

Speaking  generally,  reannealing  produces  the  reverse  effects — 
the  gradual  reappearance  of  the  a  constituent.  But  the  a 
constituent  in  a  quenched  and  reannealed  bronze  presents 
a  different  appearance  from  that  of  the  simply  annealed 
metal.  It  is  finer,  more  drawn  out,  and  retains  the  acicular 
crystallite  formation  of  the  M  constituent,  as  well  as  its  arrange- 
ment. But  the  very  fine  needles  of  the  M  constituent  are 
blunted  and  shortened  in  the  new  constituent  a.  This  leads 
to  an  increase  in  the  Shock  Resistance,  which,  owing  to  the 
exclusive  presence  of  the  constituent  M,  quenching  alone  had 
considerably  reduced. 

(d)  MICROGRAPHIC  EXAMINATION  OF  CAST  SPECIMENS. 

Microphotographs  27  and  28,  Plate  VIII,  reveal  the  presence 
of  the  constituents  a  and  E  in  cast  specimens.  Annealing 
these,  as  is  easily  seen,  has  not  any  considerable  effect — a  fact 
confirmed  by  mechanical  tests  (see  Photographs  29-32  inclu- 
sive, Plates  VIII-IX). 

The  microphotographs  33-37  inclusive,  Plate  X,  show  the 
effect  of  quenching  cast  aluminium  bronze.  After  quenching 
from  800°,  the  almost  complete  disappearance  of  the  a  con- 
stituent and  the  presence  of  M  throughout  the  mass  may  be 
observed. 

Cast  articles,  as  well  as  pressed,  acquire  by  quenching  the 
structure  shown  in  the  photographs. 

Their  mechanical  properties  are  given  in  the  appropriate 
chapter. 

H.    CUPRO- ALUMINIUM,  TYPE  II 

The  Photographs  38  and  39,  Plate  XI,  refer  to  the  alloy  of 
Type  II,  as  forged,  and  Photographs  40  and  41  refer  to  the 
same  alloy  as  annealed  after  forging.  They  show  the  same 
two  constituents  as  do  the  preceding  bronzes. 

Photographs  42  and  43,  Plate  XII,  show  the  development 
of  the  same  structure  after  quenching  from  900°  and  reannealing 
at  600°. 

III.    CUPRO -ALUMINIUM,  TYPE  III 

Plates  XIII-XVII  inclusive  refer  to  Type  III  aUoy, 
and  show  that  quenching,  whatever  the  temperature  from 


146  ALUMINIUM  AND  ITS  ALLOYS 

which    this    takes    place,    has  no   influence    on   the    micro- 
structure. 

As  we  have  seen,  this  alloy  does  not  possess  any  trans- 
formation points,  and  shows  the  same  microstructure  after 
annealing,  after  quenching,  and  after  quenching  followed  by 
reannealing. 


APPENDIX  I 
ANALYSIS  OF  ALUMINIUM 

I.   ESTIMATION  OF  ALUMINIUM,  SILICON,  AND  IRON  IN  COMMERCIAL 
ALUMINIUM. 

(a)  Estimation  of  Aluminium. 

DISSOLVE  1  gm.  of  the  metal  in  100  c.c.  hydrochloric  acid  (1  : 3) 
in  a  conical  flask  ;  when  solution  is  complete,  transfer  the  liquid 
to  a  porcelain  dish,  and  evaporate  to  dryness  on  a  sand  bath — to 
render  the  silica  insoluble. 

Take  up  in  10  c.c.  of  concentrated  hydrochloric  acid  and  100  c.c. 
of  water ;  heat  until  the  aluminium  salts  are  completely  dissolved  ; 
filter  off  the  silica,  collecting  the  filtrate  in  a  graduated  flask  of 
1  litre  capacity  ;  allow  to  cool,  and  make  up  to  the  mark  with 
distilled  water.  Pour  the  liquid  into  a  flat-bottomed  flask  of 
1J  litres  capacity,  and  shake  vigorously  to  make  the  mixture 
homogeneous. 

By  means  of  a  graduated  pipette,  transfer  200  c.c.  of  the  liquid 
into  a  conical  flask,  add  1-2  c.c.  of  nitric  acid,  and  boil  for  some 
minutes  in  order  to  oxidise  the  iron.  Add  excess  of  ammonia  and 
boil  again  until  the  smell  of  ammonia  has  completely  disappeared, 
then  add  a  few  more  drops  of  ammonia  and  filter.  Wash  the 
precipitate  carefully  with  hot  distilled  water,  dry  and  ignite. 

In  spite  of  the  ignition,  the  oxides  of  iron  and  aluminium  may 
still  contain  ammonium  salts.  To  remove  these,  powder  the  oxides 
in  an  agate  mortar — in  order  to  avoid  loss,  it  is  necessary  to  moisten 
with  a  little  water  containing  a  few  drops  of  ammonia.  Filter, 
wash,  dry,  and  ignite  strongly  for  a  quarter  of  an  hour  in  a  platinum 
crucible  over  a  compressed  air  Meker  burner.  Allow  to  cool  in 
a  desiccator  and  weigh  rapidly — calcined  alumina  being  very 
hygroscopic. 

The  weight,  thus  obtained,  represents  the  total  weight  of  the 
oxides  of  iron  and  aluminium.  From  this  weight,  subtract  the 
weight  of  oxide  of  iron,  estimated  by  the  method  given  below,  and 
thus  obtain  the  weight  of  alumina. 

(Al203xO-5302  ^aluminium). 

N.B. — Test  purity  of  silica  with  hydrofluoric  and  sulphuric 
acids. 

147 


148  ALUMINIUM  AND  ITS  ALLOYS 

(b)  Estimation  of  Iron. 

Act  upon  2  gm.  of  the  metal  with  30  c.c.  of  35  %  soda  (NaOH) 
in  a  conical  flask,  first  in  the  cold,  then  on  a  sand  bath,  until  all 
the  aluminium  is  dissolved.  Allow  to  settle,  decant  carefully, 
transfer  to  a  filter  with  distilled  water  and  wash. 

By  means  of  a  jet  of  water,  transfer  the  oxide  of  iron  to  a  conical 
flask ;  dissolve  by  the  addition  of  a  few  cubic  centimetres  of  sul- 
phuric acid  ;  reduce  by  means  of  zinc,  and  titrate  against  perman- 
ganate of  potash. 

II.    METHOD  USING  POTASH. 

Place  1  gm.  of  aluminium  in  a  conical  flask  with  10  c.c.  of  soda 
or  potash  (NaOH,  KOH).  Allow  the  reaction  to  take  place  in  the 
cold,  heating  when  it  is  nearly  completed.  Dilute  to  about  100  c.c. 
and  filter. 

The  solution  contains  the  zinc  and  aluminium,  part  of  the  tin 
and  part  of  the  silica.  The  residue  consists  of  iron,  copper,  nickel, 
manganese,  and  magnesium,  either  as  metal  or  oxide.  This  is 
washed  and  treated  with  dilute  nitric  acid  and  a  little  sulphuric 
acid.  If  tin  is  present,  evaporate  to  dryness,  take  up,  filter,  wash 
the  oxide  of  tin,  and  ignite.  This  is  only  part  of  the  tin. 

The  filtrate  is  subjected  to  electrolysis  to  estimate  the  copper, 
and  then  boiled,  and  ammonia  is  added  to  precipitate  the  iron  as 
oxide.  The  precipitate  is  dissolved  in  sulphuric  acid,  reduced  by 
zinc,  and  the  iron  is  estimated  by  titration  against  potassium 
permanganate . 

Nickel  is  estimated  by  electrolysis  of  the  ammoniacal  filtrate. 

Finally,  if  any  magnesium  is  present,  it  is  estimated  by  precipita- 
tion with  sodium  phosphate. 

The  initial  potash  solution  contains  a  portion  of  the  tin.  Acidify 
with  hydrochloric  acid,  pass  in  sulphuretted  hydrogen,  filter  and 
wash.  Treat  the  precipitate  with  nitric  acid,  ignite,  weigh,  and 
add  this  weight  to  that  of  the  tin  previously  determined. 

If  any  zinc  is  present,  boil  the  acid  filtrate  from  the  sulphides, 
neutralise  in  the  cold  with  sodium  carbonate  and  sodium  acetate, 
and  pass  in  sulphuretted  hydrogen — this  causes  the  precipitation 
of  zinc  sulphide.  Filter,  wash,  and  redissolve  in  dilute  sulphuric 
acid.  Boil  the  solution,  allow  to  cool,  add  ammonia  and  ammonium 
oxalate,  and  electrolyse. 

All  the  other  metals  having  been  accurately  determined,  alu- 
minium is  usually  obtained  by  difference. 

If  a  direct  determination  of  aluminium  is  desirable,  as  a  check, 
the  potash  solution  is  neutralised  with  hydrochloric  acid,  and  boiled 
for  about  10  mins.  The  precipitated  alumina  is  washed  by  decanta- 
tion,  filtered,  redissolved  in  nitric  acid,  reprecipitated  by  ammonia 
under  the  same  conditions,  ignited,  and  weighed. 


APPENDICES  149 

Silica. 

Treat  1  gni.  of  aluminium  with  30  c.c.  of  the  following  mixture  : — 

Nitric  acid  (1-42)  .  .  .  .100  parts 
Hydrochloric  acid  (1-2)  .  .  .  100  parts 
Sulphuric  acid  (25  %  by  volume)  .  600  parts 

in  a  vessel  covered  with  a  funnel,  evaporate  to  dryness  on  a  water 
bath,  then  on  a  sand  bath  until  white  fumes  are  given  off.  Take 
up  with  water,  filter  and  wash.  Fuse  the  precipitate,  which  con- 
sists of  silicon  and  silica,  with  an  equal  weight  of  a  mixture  of  sodium 
carbonate  and  potassium  carbonate. 

Take  up  with  dilute  hydrochloric  acid,  evaporate  to  dryness, 
filter,  wash,  ignite,  and  weigh.  The  silicon  has  been  converted  to 
silica. 

III.    ESTIMATION  OF  ALUMINA  IN  ALUMINIUM. 
Outline  of  Method. 

Pass  a  current  of  pure,  dry  chlorine  over  aluminium  heated  to 
500°,  to  convert  the  elements  aluminium,  iron,  silicon,  and  copper 
to  chlorides,  and  leave  the  alumina  and  carbon  unattacked.  The 
volatile  chlorides  are  driven  off,  and  the  others,  if  present,  are 
separated  by  washing. 

Details  of  Method. 

(a)  The  apparatus  consists  of  a  source  of  pure,  dry  chlorine, 
preferably  a  bottle  of  liquid  chlorine,  a  bubbling  flask  containing 
sulphuric  acid,  so  that  the  rate  of  delivery  can  be  regulated,  a  hard 
glass  tube,  of  30  mm.  internal  diameter  and  60  mm.  long,  with  one 
end  bent  and  dipping  into  an  empty  flask.    The  combustion  tube 
is  heated  in  a  gas  furnace. 

(b)  For  analysis,  take  1  gm.  of  fragments  or  coarse  shavings  of 
the  metal  with  clean  surface  and  not  powder  or  dust  of  which  the 
surface  is  oxidised — the  mere  use  of  aluminium  is  sufficient  to 
oxidise  it. 

The  sample  is  placed  in  a  large  porcelain  or  silica  boat,  previously 
weighed,  and  introduced  into  the  glass  tube  which  has  been 
thoroughly  dried. 

(c)  Pass  a  rapid  current  of  chlorine  for  a  quarter  of  an  hour,  so 
as  to  displace  completely  the  air  which  is  in  the  apparatus.    Warm 
gradually  to  dull  redness,  maintaining  a  steady  current  of  gas, 
watch  the  boat,  and,  as  soon  as  the  incandescence,  which  marks 
the  commencement  of  the  reaction,  is  visible,  increase  the  current 
of  chlorine  so  as  to  drive  to  the  exit  all  the  aluminium  chloride 
vapour.    When  the  incandescence  has  ceased,  reduce  the  current 
of  chlorine,  but  allow  it  to  pass  for  another  half -hour,  maintaining 
the  temperature  at  dull  redness. 


150  ALUMINIUM  AND  ITS  ALLOYS 

At  the  end  of  this  period,  stop  heating  and  allow  the  apparatus 
to  cool  in  a  current  of  the  gas  ;  when  the  tube  is  cold,  the  boat 
is  removed  and  weighed ;  the  increase  in  weight  represents  the 
alumina  and  carbon.  The  boat  is  then  heated  to  redness  to  ignite 
the  carbon,  and  after  cooling  weighed  to  give  the  weight  of  alumina, 
which  should  be  white  if  pure. 


APPENDIX  II 

Extracts  from  the  French  Aeronautical  Specifications  dealing  with 
Aluminium  and  Light  Alloys  of  great  Strength 

THE  French  Aeronautical  Specifications*  (8th  April,  1919)  prescribe 
the  following  methods  for  determining  the  physical  and  mechanical 
properties  of  aluminium  and  its  alloys. 

Pure  Aluminium  (Sheet  and  Strip). 
Tensile  and  cupping  tests  are  required. 

Light  Alloys  of  Great  Strength. 

While  the  composition  and  manner  of  working  are  left  to  the 
choice  of  the  manufacturer,  the  density  must  not  exceed  2-9,  and 
the  mechanical  properties  must  be  those  specified  below.  The  tests 
prescribed  depend  upon  the  form  in  which  the  metal  is  supplied, 
and  are  as  follows  : — 

(i)  Sheet  and  Strip  :   Tensile  and  cold  bending  tests, 
(ii)  Tubes  :  Drifting,  crushing,  and  tensile  tests, 
(iii)  Bars  and  Sections  :  Tensile  tests  only. 

TENSILE  TESTS. 

Longitudinal  and  transverse  tensile  tests  are  prescribed  in  the 
case  of  aluminium  and  aluminium  alloys  of  great  strength  of  thick- 
ness greater  than  1  mm.,  and  involve  the  determination  of  Elastic 
Limit,  Tensile  Strength,  and  %  Elongation. 

The  Elastic  Limit  is  defined  as  the  Stress,  above  which  the 
Elongation  is  permanent,  and  is  determined 

(1)  by  means  of  a  Stress /Strain  diagram,  if  possible,  giving  an 

accuracy  of  ±1  %  in  the  determination  of  the  yield  point 
and  of  the  Elongation,  or 

(2)  by  means  of  dividers,  or 

(3)  by  means  of  the  fall  or  arrest  of  the  mercury  column  or  of  the 

arrow  indicating  the  load. 

*  The  Commission  de  Standardisation  of  the  French  Minister  of  Commerce 
(Commission  A),  unification  des  Cahiers  des  charges  des  produits  metallur- 
giques  (Aluminium  and  Light  Alloys  Section  under  the  presidency  of  Lt.-Col. 
Grard)  has  drawn  up  the  French  General  Specifications  (Cahiers  des  Charges 
Unifies  Francais)  referring  to  aluminium  and  its  alloys,  for  which  the  aero- 
nautical specifications  have  served  as  a  basis.  Footnotes  are  given  where 
any  difference  exists  between  the  two  specifications. 

151 


152  ALUMINIUM  AND  ITS  ALLOYS 

If  dividers  are  used,  the  points  are  placed  in  two  gauge  marks  on 
the  test  piece,  and  the  load  is  noted  at  which  the  points  of  the 
dividers  no  longer  reach  the  marks. 

The  Tensile  Strength  is  denned  as  the  maximum  stress  supported 
by  the  test  piece  before  fracture  takes  place. 

The  Stress,  in  both  Tensile  Strength  and  Elastic  Limit  determina- 
tions, is  calculated  per  unit  area  of  cross  section  of  the  unstrained 
test  piece,  and  is  expressed  in  kilograms  per  square  millimetre. 

The  Elongation  is  measured  after  fracture,  by  placing  the  two 
ends  in  contact  and  measuring  the  final  distance  apart  of  the  gauge 
marks. 

The  gauge  marks  are  punched  on  the  unstrained  test  piece,  the 
initial  distance  between  them  being  given  by  the  formula 

L=\/66-67S    where  L  =  gauge  length  (mm.) 

S  =  initial  area  of  cross  section  (sq.  mm.) 
66-67  ^constant. 

This  length  L  should  be  marked  out  on  the  test  piece  in  two 
separate  places,  from  each  end  of  the  parallel  portion. 

The  Dimensions  of  the  Test  Pieces  for  sheet  and  strip  metal  should 
be  as  follows  : — 

"  NORMAL  "  TEST  PIECES. 

Between  shoulders.  Length,  200  mm. 
Breadth,  30  mm. 
Thickness,  that  of  the  sheet  or  strip. 

Ends.     Length,  50  mm. 
Breadth,  40  mm. 

Curved  portion  of  shoulders,  10  mm.  radius. 

These  dimensions  may  be  diminished,  but  the  length  between 
shoulders  must  be  equal  to  the  gauge  length  specified  plus  twice 
the  breadth  of  the  test  piece. 

REQUIREMENTS. 

(1)  Pure  Aluminium,  Sheet  and  Strip. 
The  following  values  should  be  obtained  : — 

(a)  Longitudinal.    Tensile  Strength  (minimum),  9  kg. /mm.2 

(5-7  tons/in.2) 
%  Elongation,  38  % 

(b)  Transverse.        Tensile  Strength  (minimum),  9  kg.  /mm.2 

(5-7  tons) 
%  Elongation,  36  %. 

But,  in  both  cases,  if  the  Tensile  Strength  exceeds  that  specified 
(9  kg. /mm.2)  by  n  kg. /mm2,  then  the  value  of  the  %  Elongation, 


APPENDICES  153 

which  will  be  required,  will  be  lower  than  that  specified  by  2n  %, 
provided  that  the  value  is  not  below  32  %. 

Example.    Longitudinal  test  piece — 

Tensile  Strength  (observed)      =  10-5. 

Then  %  Elongation  required   =38-2(1-5)  =35  %. 

(2)  Light  Alloys  of  Great  Strength. 

The  following  values  are  required  : — 
Sheet  and  Strip. 

Tensile  Strength  =38  kg.  per  sq.  mm.*  (24-1  tons  /in.2) 

Elastic  Limit        =20  kg.  per  sq.  mm.  (12-7  tons /in.2) 

%  Elongation      =14. 

Tubes.  Tensile  tests  are  carried  out  on  the  actual  tubes,  using 
steel  plugs  to  avoid  local  cracking  during  the  test.  In  the  case  of 
tubes  of  diameter  greater  than  30  mm.,  and  of  tubes  not  cylindrical, 
the  tube  is  cut  longitudinally,  flattened  out  by  means  of  a  wooden 
mallet,  and  a  test  piece  is  cut  to  the  dimensions  specified. 

The  values  required  are  : — 

Minimum  Tensile  Strength  :  36  kg.  per  sq.  mm.  (22-8  tons /in.2) 

Elastic  Limit :       20  kg.  per  sq.  mm.  (12-7  tons/in.2) 

%  Elongation  :     15  %. 

Bars  and  Sections.    The  requirements  are  as  follows  : — 
Class  (a).  Sections  >    2  mm.  thick. 

Bars        >  16  mm.    in    diameter    and<36    mm.    in 

diameter. 

Tensile  Strength  :    36  kg.  per  sq.  mm.  (22-8  tons/in.2) 
Elastic  Limit :         20  kg.  per  sq.  mm.  (12-7  tons /in.2). 

For  bars>36  mm.  in  diameter  : — 

Tensile  Strength  :    33  kg.  per  sq.  mm.  (20-9  tons/in.2) 
Elastic  Limit :          19  kg.  per  sq.  mm.  (12-1  tons /in.2) 
%  Elongation  :        13  %. 

Class  (6).    Sections < 2  mm.  thick. 

Bars  (specified  Drawn)  of  any  diameter  and  bars <  16  mm.  in 

diameter. 

Tensile  Strength  :    38  kg.  per  sq.  mm.  (24-1  tons  per  sq.  in.) 
Elastic  Limit :         22  kg.  per  sq.  mm.  (14-0  tons  per  sq.  in.) 
%  Elongation  :       16  %,  or   14  %  in  the  case  of  bars  and 
sections   so   thin   that   straightening   is 
necessary. 
CUPPING  TESTS. 

Cupping  tests  are  required  for  pure  aluminium,  sheet  and  strip. 
The  prescribed  method  is  that  described  on  page  41  ,  and  the 

*  The  Cahiers  des  Charges  Unifies  Fran£ais  specify  a  minimum  Tensile 
Strength  of  36  kg./mm.»  (22-8  tons /in8.). 


154  ALUMINIUM  AND  ITS  ALLOYS 

following  minimum  depth    of  impression  at   rupture  should  be 
obtained  : — 

Thickness          .          .     0-5  mm.       1-0  mm.       1-5  mm.  2-0  mm. 

•020  in.        -039  in.        -059  in.  -079  in. 

Depth  of  impression  .   llmm.        13mm.        14mm.  15mm. 

Cold  Bending  Tests  are  prescribed  for  light  alloy  sheet  and 
strip,  and  the  following  method  should  be  adopted  wherever 
possible  : — 

The  test  is  carried  out  at  ordinary  temperatures,  and  in  a  special 
machine  giving  a  gradually  increasing  pressure,  without  shock. 
The  bend  is  formed  in  two  operations. 

First  Operation.  The  test  piece,  which  should  be  100  mm.X 
20  mm.  if  possible,  is  placed  on  a  V-shaped  block,  whose  surfaces  are 
inclined  to  each  other  at  an  angle  of  60°  ;  the  opening  should  be 
125  mm.  at  least.  A  wedge  (whose  edge  should  be  rounded  off  with 
a  radius  at  least  equal  to  that  which  the  bend  should  have  at  the 
completion  of  the  test)  is  applied  to  the  middle  of  the  test  piece,  and 
depressed  mechanically  until  the  test  piece  is  in  contact  with  the 
faces  of  the  V. 

Second  Operation.  Using  a  spacer,  the  test  piece  should  be  bent 
slowly,  by  mechanical  means,  into  the  form  of  the  letter  U.  No 
cracks  should  appear.  The  distance  between  the  two  interior 
surfaces  of  the  arms  of  the  U  is  specified  in  the  following  table  : — 

Thickness*  Longitudinal.  Transverse. 

Less  than  1-5  mm.  (-059  in.)      SJxthickness        4xthickness 
=or>l-5mm.  (-059in.)  4   xthickness        Sxthickness 

Drifting  Tests.    Prescribed  for  light  alloy  tubes. 

A  conical,  hardened  steel  mandrel,  having  an  angle  of  45°,  is 
forced  axially  into  a  short  length  of  tube  until  the  first  split  appears. 
This  should  not  occur  until  the  diameter  has  increased  by  11  %.| 

Crushing  Tests.    Prescribed  for  light  alloy  tubes. 

A  short  length  of  tube  is  flattened  by  means  of  a  hammer  moving 
in  a  direction  parallel  to  the  principal  axis.  The  tube  is  supported 
on  a  piece  of  steel  to  avoid  localisation  of  stress.  No  fissure  should 
appear  until  the  reduction  in  length  of  the  principal  axis  of  the 
tube  has  reached  or  exceeded  40  %. 

*  The  Cahiers  des  Charges  Unifies  Frangais  specify  the  following  dis- 
tances : 

Thickness.          Longitudinal.  Transverse. 

<  1  -5  mm.        4-5  x  thickness         5  X  thickness 

=  or>  1  -5  mm.        5-5  X  thickness         6  X  thickness 

f  Cahiers  Unifies  Fran§ais  specify  9  %. 


APPENDIX  III 


LAB  OR  AT  GERE  D'ESSAIS 
MECANIQUES,  PHYSIQUES, 
CHIMIQUES  ET  DE  MACHINES. 

292  Rue  Saint  Martin,  Paris. 


REPUBLIQUE  FRANC  AISE. 
Ministere  du  Commerce,  de  Tin* 
dustrie,  des  Postes  et  des  Tele- 
graphes. 

Conservatoire  des  Arts  et  Metiers. 
Paris,  Feb.  5th,  1919. 


Report  of  Test  No.  13456  on  the  requisition  of  Major  Grard, 
technical  inspector  of  metallurgical  aviation  materials,  Paris. 

Registered,  Jan.  18th,  1919. 

Object.    Tensile  and  Shock  tests  at  a  temperature  of  15°  on  test 
pieces  of  sheet  aluminium  possessing  various  degrees  of  cold  work. 

RESULTS. 
Dimensions  of  test  pieces. 

(a)  Tensile  Test  Pieces. 

(Length        ;         .         .  100mm. 
Between  shoulders    -/Breadth      .         *  ••      .     15mm. 
(Thickness    .         .         ,{   10  mm. 
Approximate  area  of  cross  section          .          .   150  sq.  mm. 

(accurately  measured  for  each  test  piece) 
Gauge  length  =  ^66-678       .  .'*         .        =  100mm. 

(b)  Shock  Test  Pieces. 

Bars  :   55x10x10  mm.  with  a  2-mm.  round  notch. 
Apparatus  :  30  kg.  m.    Charpy  pendulum. 


155 


156 


ALUMINIUM  AND  ITS  ALLOYS 


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APPENDIX  IV 

LABORATOIBE  D'ESSAIS  REPUBLIQUE  FRANQAISE. 

MECANIQUES,  PHYSIQUES,          Ministere  du  Commerce,  de  Tin 
CHIMIQUES  ET  DE  MACHINES.       dustrie,  des  Postes  et  des  Tele- 

graphes. 

Conservatoire  des  Arts  et  Metiers. 
Paris,  Jan.  2±th,  1919. 

Report,  No.  7,  of  Test  No.  13357  on  the  requisition  of  Major  Grard, 
technical  inspector  of  metallurgical  aviation  materials,  Paris. 

Registered,  Nov.  27th,  1918. 

Object.  Tensile  tests  on  test  pieces  of  sheet  aluminium  after 
thermal  treatment. 

NATURE  OF  SAMPLES  SUBMITTED. 

Two  series  of  tensile  test  pieces  in  sheet  aluminium  :  — 

(1)  0-5  mm.  thick  marked   5. 

(2)  2-0  mm.  thick  marked  20. 

Each  of  these  series  consists  of  metal  having  three  degrees  of  cold 

work,  namely  :  —  rt  n/  ,     ,  ^ 

J  50  %    marked  B. 

100  %     marked  C. 
300  %    marked  D. 

Metal  of  each  of  the  above  thicknesses  and  degrees  of  cold  work 
has  been  annealed  under  the  following  conditions  :  — 

All  the  test  pieces  requiring  the  same  anneal  were  pierced  with 
a  hole  at  one  end  and  threaded  on  to  the  same  piece  of  wire,  6-8  mm. 
apart,  so  as  to  be  immersed  simultaneously  in  the  annealing  bath, 
which  was  continuously  stirred. 

Sheets  40  mm.  square  and  circles  90  mm.  in  diameter,  for  micro- 
graphic  examination  and  cupping  tests  respectively,  were  subjected 
to  the  same  anneal  at  the  same  time  as  the  tensile  test  pieces. 

RESULTS. 

Dimensions  of  Test  Pieces. 


Between  shoulders   I  *f  "^J1,        '         '   ™  mm' 
{  Breadth       .          .     20  mm. 

Approximate  area  of  cross  section  :  —  * 

(1)  Test  pieces  0-5  mm.  thick         .          .     10  sq.  mm. 

(2)  Test  pieces  2-0  mm.  thick         .          .     40  sq.  mm. 

Gauge  length  =<\/Gfr~61S  :— 

(1)  Test  pieces  0-5  mm.  thick  —  gauge  length  =30  mm. 

(2)  Test  pieces  2*0  mm.  thick—  gauge  length  =50  mm. 

*  In  each  case  the  breadth  and  thickness  were  measured  to  the  nearest 
•01  mm.,  and  the  exact  cross  section  calculated  from  these  figures. 

158 


APPENDICES 


159 


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O  O  O 
CS  CS  CM 

O   O   CO               ,     r-H   O 

000               00 

CO   T*    TjH               '     O    »O 

(M  O  CO  •*  OS 
O  O  OS  T*<  OS 

I-H    1—  1    F-(    (M    <>) 

CO  O  O  <M         CO  O 
0  r*  0  OS         -*  0 
CO  T*  T*  •*         0  CD 

ia 

b 

1      1      I 

CS  O  O         O  35  <M 
Cl  O  O         Tf  -^  O 
CO  "*  -^         O  O  O 

^   ,—1   O   O    PH 

O  0  05  -*  0 

^H   ^(  r-4   <M    CO 

O  O  CO  GO         O  O 
0  -H  0  OS         00 
CO  ^  •*  •*         O  O 

0 

§t-  IT- 
O  O 
<M  (M  «N 

O  <N  <-i         OS  O  00 

0    O   rM            T*    0    0 

Tii  T*  <<#         O  O  O 

<M  CO  i—  I  O  •* 

o  o  o  o  o 

i—  i  I-H  <M  (M  CO 

CO  O  O  O        O  CO 

O  !M   CC  f-«           O   •—  I 

CO  TJ<  •*  O         O  O 

Kequired 
temperature 

(degrees  C.) 

§ 
CM 

§       § 

rj<                     U5 

8§§§8 

^H  ^H  (^  <M  CO 

§iii  §§ 

CO  •<*  T*I  O         O  O 

Duration 

I 

3 
| 

5<l  O  O 

•9 

F^CO  O        6  f-i  <N 

»O 

CO                    1-1 

x 
1 

0 

•£ 

0 

-*3 

4 

I 

i 

"1 

160 


ALUMINIUM  AND  ITS  ALLOYS 

A.     PRELIMINARY  TESTS  * 


Anneal 

Apparent 
Elastic  Limit 

Tensile 
Strength 

Elonga- 

T? A 

Temperature 
(degrees  0.) 

Duration 
(minutes) 

Marks 

Kg          tons 
mm*         in* 

Kg         tons 
mm*         in1 

tion 

% 

JK6- 

marks 

/B1 

11-1       7-05 

12-7       8-06 

6-0 

(2) 

[  B2 

11-3       7-18 

13-7       8-70 

12-7 

(2) 

-  \  Cl 

10-4       6-60 

14-2       9-02 

12-7 

0     C2 

11-0       6-98 

15-1       9-59 

16-3 

Dl 

11-5       7-80 

15-8     10-03 

6-0 

(1) 

203-0° 

2 

\D2 
/B1 

10-4       6-60 
9-8       6-22 

15-9     10-09 
11-9       7-56 

4-0 
16-4 

(1) 

(m 

9-45     6-00 

11-4       7-24 

15-0 

9n)cl 

6-85     4-35 

12-8       8-23 

16-6 

20    C2 

8-65     6-49 

13-0       8-26 

15-0 

Dl 

13-2       8-35 

15-4       9-78 

10-0 

XD2 

12-9       8-19 

15-2       9-65 

9-8 

B3 

11-5       7-30 

13-5      8-57 

16-0 

(1) 

B4 

9-9       6-29 

13-2       8-38 

11-6 

K     C3 

12-0       7-62 

13-9       8-83 

16-6 

5     C4 

12-3       7-81 

14-4       9-14 

16-0 

D3 

13-3       8-45 

15-8     10-03 

10-0 

208-5° 

5 

D4 

13-3       8-45 

15-7       9-97 

10-0 

,B3 

9-6       6-10 

11-5       7-30 

16-0 

(B4 

9-4       5-97 

12-1       7-68 

16-0 

90JC3 

10-2       6-48 

12-8       8-13 

16-0 

-U)C4 

10-9       6-92 

12-8       8-13 

17-4 

(D3 

11-9       7-56 

14-7       9-30 

10-0 

VD4 

11-0       6-98 

14-8       9-40 

10-0 

(1) 

B5 

11-0       6-98 

13-2       8-38 

12-7 

(1) 

B6 

11-7       7-43 

15-3       9-72 

16-0 

K     C5 

10-8       6-86 

14-3       9-08 

15-0 

5     C6 

10-7       6-79 

15-5       9-84 

16-0 

Do 

11-0       6-98 

16-3     10-35 

11-7 

203-5° 

10 

D6 

14-0       8-89 

15-5       9-84 

9-7 

B5 

10-1       6-41 

11-9       7-56 

18-2 

B6 

9-1       5-78 

11-8       7-49 

18-2 

90      C5 

10-9       6-92 

12-7       8-06 

17-0 

20    C6 

11-6       7-37 

12-7       8-06 

18-8 

D5 

12-4       7-87 

14-7       9-33 

10-0 

D6 

11-5       7-30 

15-0       9-52 

11-8 

*  These  tests  have  been  carried  out  with  a  view  to  investigating  the 
minimum  length  of  time  necessary  for  complete  anneal  at  any  given  tempera- 
ture, using  test  pieces  of  any  given  thickness. 

As  a  result  of  these  preliminary  tests,  the  following  experimental  condi- 
tions have  been  adopted  for  both  types  of  test  piece  : 

Temperature  and  anneal.         Duration  (minutes). 
150°— 300°(inclusive)  5 

350°— 500°       „  3 

550°— 600°       „  1 

Remarks. — (1)  Broken  outside  gauge  length. 
(2)  Broken  on  gauge  mark. 


APPENDICES 

A.    PRELIMINARY  TESTS — continued 


161 


Anneal 

Apparent 
Elastic  Limit 

Tensile 

Strength 

Elonga- 

-¥>— _ 

Temperature 
(degrees  C.) 

Duration 
(minutes) 

Marks 

Kg         tons 
mm*           in* 

Kg         tons 
mm*           in* 

tion 
% 

J\C* 

marks 

B7 

5-5         3-49 

11-2       7-11 

35-0 

. 

B8 

3-9         2-48 

10-8       6-86 

31-7 

C7 

4-1         2-60 

12-5       7-94 

33-4 

(2) 

C8 

4-3         2-73 

12-1       7-68 

40-0 

D7 

4-4         2-79 

11-8       7-49 

36-6 

D8 

3-8         2-41 

12-0       7-62 

36-0 

398° 

1 

,B7 

3-4         2-16 

9-8       6-22 

38-6 

I  B8 

3-6         2-29 

9-9       6-29 

38-0 

on)C7 

3-5         2-22 

10-2       6-48 

37-4 

20    C8 

3-0         1-90 

10-2       6-48 

44-0 

(D7 

31         1-97 

10-6       6-73 

40-0 

VD8 

3-4        2-16 

10-6      6-73 

37-0 

B9 

5-2         3-30 

10-1       6-41 

34-4 

(BIO 

43         2-73 

10-9       6-92 

33-3 

*JC9 

54        343 

11-2       7-11 

36-4 

°icio 

5-2         3-30 

11-8       7-49 

36-7 

D9 

4-0         2-54 

11-6      7-37 

35-0 

VD10 

4-7         2-98 

11-7       7-43 

38-4 

403° 

3 

B9 

31         1-97 

9-7       6-16 

38-6 

BIO 

3-0         1-90 

9-7      6-16 

36-8 

9ft 

C9 

3-0         1-90 

10-4       6-60 

40-4 

/U 

CIO 

2-6         1-65 

10-4       6-60 

38-4 

D9 

34         2-16 

10-8       6-86 

38-0 

XD10 

36         2-29 

10-8       6-86 

364 

Bll 

5-1         324 

11-5       7-30 

36-0 

B12 

4-8         3-05 

114       7-24 

333 

Cll 

49         3-11 

11-7       7-43 

34-0 

C12 

53         337 

12-2       7-75 

38-4 

Dll 

34         2-16 

11-4       7-24 

38-4 

D12 

3-6         2-29 

11-5       7-30 

37-0 

393° 

5 

Bll 

31         1-97 

9-6       6-10 

39-0 

B12 

2-9         1-84 

9-7       6-16 

39-0 

9ft 

Cll 

3-4         2-16 

10-6       6-73 

39-4 

4() 

C12 

4-2         2-67 

10-8       6-86 

41-0 

Dll 

3-6         2-29 

10-7       6-79 

36-0 

D12 

3-8         2-41 

10-8       6-86 

36-4 

XB13 

3-9         2-48 

11-6       7-37 

333 

[  B14 

33         2-10 

11-5       730 

32-6 

)C13 

4-2         2-67 

11-8       7-49 

36-8 

5)C14 

3-4         2-16 

11-7       7-43 

36-8 

[D13 

32         2-03 

11-1       7-05 

384 

VD14 

3-8         2-41 

11-2       7-11 

36-8 

549° 

0-5 

B13 

2-8         1-78 

9-9       6-29 

39-6 

B14 

3-1         1-97 

10-2       6-48 

38-0 

9ft 

C13 

3-2         2-03 

11-1       7-05 

37-8 

Z\J 

C14 

3-6         2-29 

10-8       6-86 

34-0 

D13 

31         1-97 

10-9       6-92 

39-6 

D14 

33         2-10 

10-9       6-92 

37-0 

162 


ALUMINIUM  AND  ITS  ALLOYS 

A.    PRELIMINARY  TESTS— continued 


Am 

Temperature 
(degrees  C.) 

leal 

Duration 
(minutes) 

Marks 

Apparent 
Elastic  Limit 

Kg         tons 

Tensile 
Strength 

Kg         tons 

Elonga- 
tion 

% 

Re- 
marks 

mm3         in2 

mm*        in2 

.B15 

4-2       2-67 

11-2       7-11 

34-4 

[B16 

4-1       2-60 

11-0       6-98 

34-4 

6\C15 

4-8       3-05 

11-7       743 

35-0 

°5  C16 

3-8       2-41 

12-3       7-81 

31-7 

f  D15 

3-7       2-35 

12-0       7-62 

34-4 

550° 

1 

\D16 
,B15 

5-0       3-17 
2-9       1-84 

11-6       7-34 
10-2       6-48 

35-0 
38-6 

(BIG 

2-8       1-78 

10-0       6-35 

36-0 

20)ci5 

3-3       2-10 

11-0       6-98 

32-0 

^U)C16 

3-4       2-16 

11-3       7-18 

36-0 

f  D15 

3-2       2-03 

10-9       6-92 

39-0 

VD16 

31       1-97 

10-8       6-86 

356 

B17 

5-0      3-17 

11-8       7-49 

33-3 

[B18 

4-8       3-05 

12-2       7-75 

32-7 

5)C17 

5-0       3-17 

13-2       8-38 

33-3 

5)C18 

4-7       2-98 

11-9       6-56 

30-0 

f  D17 

4-4       2-79 

11-5       7-30 

35-0 

551° 

2 

VD18 

4-4      2-79 

11-8       7-49 

37-4 

B17 

2-9       1-84 

10-1       6-41 

35-6 

B18 

2-6       1-65 

9-9       6-29 

36-6 

20    C17 

2-8       1-78 

11-3       7-18 

35-6 

ZU    C18 

3-2       2-03 

11-2       7-11 

35-0 

D17 

3-3      2-10 

11-0       6-98 

36-0 

D18 

3-4       2-16 

11-0       6-98 

41-6 

B.     FINAL  EXPERIMENTS 


Am 

Temperature 
(degrees  C.) 

ical 

Duration 
(minutes) 

Marks 

Apparent 
Elastic  Limit 

Kg         tons 
mm8        in* 

Tensile 
Strength 

Kg         tons 
mm2        in* 

Elonga- 
tion 
% 

Be- 
marks 

B64 

13-4       8-51 

13-9       8-83 

6-7 

B65 

13-1       8-32 

14-5       9-21 

9-7 

B66 

13-3       8-45 

14-6       9-27 

12-7 

C64 

14-3       9-08 

15-1       9-59 

11-7 

5 

C65 

14-4       9-14 

15-4       9-78 

12-3 

C66 

13-8       8-76 

15-4       9-78 

10-0 

(1) 

D64 

17-3     10-99 

17-3     10-99 

33 

(1) 

D65 

17-0     10-79 

17-0    10-79 

6-0 

Zero 
metal 
unannealed 

D66 
/B64 
B65 

17-8     11-30 
11-5       7-30 
11-4       7-24 

17-8     11-30 
12-0       7-62 
12-2       7-75 

6-3 
10-0 
11-0 

B66 

11-4       7-24 

12-4       7-87 

10-6 

C64 

13-1       8-32 

13-7       8-70 

14-4 

20^ 

C65 

12-8       8-13 

13-8       8-76 

11-2 

C66 

13-0      8-25 

13-4       8-51 

11-6 

D64 

15-8     10-03 

16-3     10-35 

7-0 

D65 

15-9     10-10 

16-6     10-54 

8-0 

D66 

15-5       9-84 

17-2     10-92 

6-6 

APPENDICES 

B.    FINAL  EXPERIMENTS — continued 


163 


Apparent 

Tensile 

Anneal 

Elastic  Limit 

Strength 

Elonga- 

T? Q 

Temperature 
(degrees  C.) 

Duration 
(minutes) 

Marks 

Kg         tona 
mm*         In* 

Kg         tona 
mm*         in* 

tion 

% 

Jtv6" 

marks 

rB31 

12-9       8-19 

14-0       8-89 

12-7 

B32 

13-8       8-76 

13-8       8-76 

130 

B33 

13-1       832 

15-4       9-78 

133 

C31 

14-8      9-40 

14-8       9-40 

11-7 

5- 

C32 

14-5      9-21 

15-0       9-52 

10-0 

C33 

14-2       9-02 

14-6       9-27 

8-3 

(1) 

D31 

17-1     10-87 

17-6     11-18 

6-0 

D32 

15-4       9-78 

15-4      9-78 

33 

ID33 

16-9     10-73 

17-3     10-99 

5-0 

(1) 

103° 

5 

fB31 

11-5       7-30 

12-0      7-62 

13-6 

B32 

11-1       7-05 

12-0      7-62 

14-0 

B33 

11-1       7-05 

12-0      7-62 

12-0 

C31 

12-1       7-68 

13-5       8-57 

14-6 

20- 

C32 

12-4       7-87 

13-7       8-70 

10-0 

(1) 

C33 

12-4       7-87 

13-6      8-64 

13-0 

D31 

14-9       9-46 

16-0     10-16 

7-6 

(1) 

D32 

13-9       8-83 

15-8     10-03 

6-0 

(1) 

D33 

13-7       8-70 

16-0    10-16 

6-0 

(1) 

fB34 

12-1       7-68 

13-4       8-51 

133 

B35 

13-8       8-76 

13-6      8-64 

15-0 

B36 

13-0      8-25 

13-48     8-56 

15-0 

C34 

10-4       6-60 

14-7      9-33 

10-0 

5- 

C35 

13-5      8-57 

14-6      9-27 

10-0 

C36 

12-9       8-19 

14-9      9-46 

63 

(1) 

D34 

12-5      7-94 

16-13  10-24 

33 

(1) 

D35 

13-9       8-83 

14-5      9-21 

33 

(1) 

160° 

5 

ID36 
'B34 

12-3       7-81 
10-6      6-73 

14-9      9-46 
12-1       7-68 

33 
13-6 

(1) 

B35 

10-9       6-92 

12-4      7-87 

14-0 

B36 

10-6       6-73 

12-0      7-62 

13-6 

C34 

12-1       7-68 

13-0      8-25 

U-0 

20  - 

C35 

11-7       7-43 

13-1       8-32 

15-0 

C36 

11-5      7-30 

133       845 

12-0 

D34 

12-9       8-19 

15-4      9-78 

8-2 

D35 

14-0       8-89 

15-6      9-91 

6-2 

(1) 

.D36 

13-2      8-38 

15-5      9-84 

7-4 

fB37 

12-0      7-62 

12-2       7-75 

153 

B38 

11-5      7-30 

13-2       8-38 

16-6 

B39 

11-8       7-49 

13-2       8-38 

10-4 

(1) 

C37 

13-0       8-25 

14-4       9-14 

10-0 

(1) 

5. 

C38 

13-4       8-51 

15-2       9-65 

15-0 

(1) 

C39 

13-4       8-51 

14-1       8-95 

7-7 

D37 

13-7       8-70 

16-5     10-48 

6-7 

(1) 

D38 

14-2       9-02 

17-6     11-18 

73 

199° 

5 

D39 

13-5       8-57 

17-0     10-79 

5-0 

(1) 

rB37 

9-6      6-10 

11-5      730 

16-2 

B38 

10-3       6-54 

12-0       7-62 

16-0 

B39 

10-0      6-35 

11-6      737 

16-2 

C37 

12-0      7-62 

13-0       8-25 

18-0 

20- 

C38 

12-0      7-62 

13-2       8-38 

16-4 

C39 

11-0       6-98 

12-8       8-13 

17-6 

D37 

13-8       8-76 

15-4       9-78 

10-0 

D38 

13-2       8-38 

15-3       9-72 

8-0 

iD39 

13-9       8-83 

15-3       9-72 

9-0 

164 


ALUMINIUM  AND  ITS  ALLOYS 

B.    FINAL  EXPERIMENTS — continued 


Anneal 

Apparent 
Elastic  Limit 

Tensile 
Strength 

Elonga- 

Re- 

Temperature 
(degrees  C.) 

Duration 
(minutes) 

Marks 

KK         tons 
mmz        in2 

Kg         tons 
mmz         in2 

tion 
% 

marks 

/B40 

11-6       7-37 

13-5       8-57 

19-3 

B41 

11-1       7-05 

12-5       7-94 

19-3 

B42 

11-2       7-11 

134       8-51 

20-0 

C40 

12-5       7-94 

12-8       8-23 

10-3 

(1) 

5< 

C41 

10-5       6-67 

13-5       8-57 

17-3 

C42 

11-8       7-49 

13-3       8-45 

19-3 

D40 

14-0       8-89 

14-0       8-89 

10-7 

(1) 

D41 

12-6       8-06 

14-6       9-27 

11-0 

<D42 

14-7       9-33 

15-3       9-72 

12-0 

244° 

5 

/B40 

9-7       6-16 

11-3       7-18 

17-6 

B41 

10-2       6-48 

11-3       7-18 

18-0 

B42 

10-0       6-35 

11-5       7-30 

17-0 

C40 

11-7       7-43 

12-6       8-00 

21-8 

20< 

C41 

10-8       6-86 

12-5       7-94 

21-0 

C42 

11-2       7-11 

12-3       7-81 

22-0 

D40 

13-1       8-32 

14-5       9-21 

12-2 

D41 

12-2       7-75 

14-4       9-14 

12-0 

<D42 

12-1       7-68 

14-2       9-02 

13-6 

/B43 

10-8       6-86 

13-1       8-32 

27-3 

B44 

10-4       6-60 

11-9       7-56 

22-7 

B45 

9-6       6-10 

12-1       7-68 

23-3 

C43 

7-0       4-44 

11-3       7-18 

35-0 

5< 

C44 

6-3       4-00 

10-7       6-79 

33-3 

C45 

6-8       4-32 

10-8       6-86 

38-3 

D43 

5-9       3-68 

10-2       6-48 

39-3 

D44 

6-0       3-75 

11-0       6-98 

38-3 

^D45 

6-5       4-13 

10-9       6-92 

41-9 

299° 

5 

B43 

8-8       5-59 

10-7       6-79 

20-4 

B44 

8-8       5-59 

10-6       6-73 

23-6 

B45 

9-0       5-71 

10-6       6-73 

23-4 

C43 

5-7       3-56 

10-4       6-60 

33-0 

20 

C44 

6-8       4-32 

10-3       6-54 

32-0 

C45 

5-9       3-68 

10-3       6-54 

34-0 

D43 

8-3       5-27 

12-0       7-62 

26-0 

D44 

7-9       5-01 

12-0       7-62 

26-0 

D45 

8-4      5-33 

11-8       7-49 

24-4 

B46 

5-3       3-37 

11-1       7-05 

35-0 

B47 

5-0      3-17 

10-2       6-48 

36-0 

B48 

6-1       3-87 

10-8       6-86 

333 

C46 

4-9       3-11 

10-8       6-86 

40-0 

5. 

C47 

4-4       2-79 

10-6       6-73 

29-7 

C48 

4-8       3-05 

11-2       7-11 

37-3 

D46 

4-6       2-92 

10-8       6-86 

41-6 

D47 

5-0      3-17 

11-1       7-05 

41-6 

354° 

Q 

D48 

5-6      3-49 

10-9       6-92 

39-0 

o 

B46 

4-4       2-79 

9-4       5-97 

37-0 

B47 

4-5       2-86 

9-4       5-97 

34-0 

B48 

5-4       3-43 

9-6       6-10 

35-0 

C46 

43      2-73 

9-9       6-29 

44-0 

20^ 

C47 

4-4      2-79 

10-0       6-35 

44-4 

C48 

4-9       3-11 

10-0       6-35 

44-4 

D46 

4-8      3-05 

10-4       6-60 

42-0 

D47 

4-4       2-79 

10-9       6-92 

41-0 

D48 

4-9       3-11 

10-2       6-48 

41-2 

APPENDICES 

B.    FINAL  EXPERIMENTS — continued 


165 


Anneal 

Apparent 
Elastic  Limit 

Tensile 
Strength 

Elonga- 

T?p- 

Temperature 
(degrees  C.) 

Duration 
(minutes) 

Marks 

Kg         tons 

mm*           in* 

Kg         tons 
mm1         in* 

tion 
% 

i\  e- 
marks 

,B49 

4-7         2-98 

10-8       6-86 

34-6 

B50 

5-5         3-49 

10-9       6-92 

32-7 

B51 

5-7         3-62 

10-8       6-86 

34-0 

C49 

4-8         3-05 

10-9       6-92 

36-6 

5, 

C50 

5-2         3-30 

11-2       7-11 

36-6 

Col 

5-2         3-30 

11-1       7-05 

383 

D49 

5-3         337 

11-6       7-37 

37-0 

D50 

5-5         3-49 

11-0       6-98 

38-4 

.D51 

5-6         3-56 

10-5       6-67 

373 

411° 

3 

,     . 

B49 

4-4         2-79 

9-7       6-16 

38-0 

B50 

4-5         2-86 

9-7       6-16 

38-4 

B51 

4-4         2-79 

9-6      6-10 

38-4 

C49 

4-9         3-11 

10-5      6-67 

41-0 

20< 

C50 

5-1         3-24 

10-6      6-73 

39-6 

C51 

4-8         3-05 

10-4       6-60 

39-6 

D49 

5-1         3-24 

10-7       6-79 

38-0 

D50 

4-9         3-11 

10-7       6-79 

38-0 

D51 

5-0         3-17 

10-7       6-79 

37-6 

,B52 

5-1         3-24 

10-7       6-79 

32-7 

B53 

5-1         3-24 

10-9       6-92 

35-0 

B54 

5-5         3-49 

10-8       6-86 

35-0 

C52 

5-5         3-49 

113      7-18 

36-7 

5 

C53 

5-9         3-75 

11-2       711 

37  7 

C54 

5-7         3-62 

116      7-37 

35-0 

D52 

5-5         3-49 

11-0       6-98 

37-3 

D53 

5-2         3-30 

11-1       7-05 

36-7 

VD54 

5-5         3-49 

11-5       7-30 

36-7 

452° 

3 

/B52 

3-4         2-16 

10-1       6-41 

37-6 

B53 

3-3         2-10 

9-8       6-22 

36-4 

B54 

36         2-29 

9-5       6-03 

36-4 

C52 

3-9        2-48 

10-9       6-92 

37-6 

20< 

C53 

4-5         2-86 

10-9       6-92 

37-2 

C54 

4-8         3-05 

10-4       6-60 

36-4 

D52 

3-9         2-48 

11-0      6-98 

36-0 

D53 

4-1         2-60 

11-0       6-98 

35-4 

VD54 

4-6         2-92 

11-1       7-05 

37-8 

/B55 

4-5         2-86 

11-4       7-24 

24-0 

B56 

53         337 

11-2       7-11 

333 

B57 

4-9         3-11 

113       7-18 

333 

C55 

4-1         2-60 

10-9       6-92 

333 

5 

C56 

4-7         2-98 

11-4       7-24 

34-0 

C57 

4-6         2-92 

11-1       7-05 

37-4 

D55 

54        3-43 

11-6       7-37 

35-0 

D56 

64         4-06 

11-3       7-18 

37-6 

496° 

3 

VD57 

6-4         4-06 

11-6       7-37 

35-6 

/B55 

3-5        2-22 

9-6       6-10 

37-6 

B56 

3-5         2-22 

9-7       6-16 

38-0 

B57 

34        2-16 

9-8       6-22 

35-0 

C55 

4-0         2-54 

11-0       6-98 

35-0 

20 

C56 

3-6         2-29 

10-5       6-67 

37-2 

C57 

3-1         197 

10-9       6-92 

36-0 

D55 

4-6         2-92 

11-3       7-18 

35-4 

D56 

4-0         2-54 

11-2       711 

36-0 

^D57 

4-9         311 

11-4       7-24 

35-6 

166 


ALUMINIUM  AND  ITS  ALLOYS 

B.    FINAL  EXPERIMENTS — continued 


Anneal 

Apparent 
Elastic  Limit 

Tensile 
Strength 

Elonga- 

"Do 

Temperature 
(degrees  C.) 

Duration 
(minutes) 

Marks 

Kg         tons 
mm*         in2 

Kg         tons 
mm2         in8 

tion 

% 

.tvG- 

marks 

B58 

4-2         2-67 

12-3       7-81 

28-3 

(i) 

B59 

4-2         2-67 

11-8       7-49 

27-4 

B60 

4-9         3-11 

11-3       7-18 

30-7 

C58 

5-2         3-30 

11-2       7-11 

35-7 

5 

C59 

4-7         2-98 

12-7       8-06 

33-3 

C60 

5-7         3-62 

11-5       7-30 

35-0 

D58 

5-6         3-56 

11-9       7-56 

36-7 

D59 

5-0         3-17 

11-4       7-24 

35-7 

D60 

4-7         2-98 

11-1       7-05 

36-3 

•552° 

1 

B58 

3-6         2-29 

9-7       6-16 

38-6 

B59 

3-6        2-29 

9-7       6-16 

38-0 

B60 

3-5         2-22 

10-0       6-35 

36-6 

C58 

4-0         2-54 

11-1       7-05 

36-4 

20 

C59 

4-0         2-54 

11-2       7-11 

34-0 

C60 

4-1         2-60 

11-5       7-30 

34-0 

D58 

4-2         2-67 

11-1       7-05 

38-0 

D59 

3-9         2-48 

11-1       7-05 

37-0 

D60 

4-1         2-60 

11-0       6-98 

36-4 

B61 

5-6         3-56 

11-4       7-24 

31-7 

B62 

4-2         2-67 

11-8       7-49 

27-4 

B63 

5-1         3-24 

12-1       7-68 

31-7 

C61 

4-7         2-98 

12-4       7-87 

24-0 

5< 

C62 

4-8         3-05 

12-2       7-75 

32-7 

C63 

5-2         3-30 

12-5       7-94 

34-0 

D61 

6-0         3-81 

11-8       7-49 

34-0 

D62 

5-7         3-62 

11-4       7-24 

35-0 

•604° 

1 

D63 

5-6         3-56 

11-8       7-49 

36-0 

B61 

3-1         1-97 

10-1       6-41 

38-4 

B62 

3-3        2-10 

10-0       6-35 

37-0 

B63 

3-7         2-35 

10-0       6-35 

36-4 

C61 

34         2-16 

11-0       6-98 

34-4 

20. 

C62 

4-0         2-54 

11-2       7-11 

35-0 

C63 

3-9         2-48 

11-3       7-18 

36-2 

D61 

4-1         2-60 

11-1       7-05 

41-0 

D62 

3-3         2-10 

11-1       7-05 

35-0 

D63 

3-9         2-48 

11-1       7-05 

40-0 

APPENDIX   V 

LABORATOIRE  D'ESSAIS  REPUBLIQUE  FRA^AISE. 

MECANIQUES,  PHYSIQUES,          Ministere  du  Commerce,  de  Fln- 
CHIMIQUES  ET  DE  MACHINES.        dustrie,  des  Posies  et  des  Tele- 

graphes. 

Conservatoire  des  Arts  et  Metiers. 
Paris,  March  I2th,  1919. 

Report  of  Test  No.  13463  on  the  requisition  of  Major  Grard, 
technical  inspector  of  metallurgical  aviation  materials,  Paris. 

Registered,  Jan.  29th,  1919. 

Object.  Tensile  and  Shock  tests  on  test  pieces  of  aluminium 
subjected  to  thermal  treatment. 

NATURE  OF  SAMPLES  SUBMITTED. 

A  series  of  tensile  and  a  series  of  shock  test  pieces.    Each  series 
consists  of  metal  having  two  degrees  of  cold  work,  namely  : — 
100  %    marked  Bx. 
300  %    marked  B2. 

Metal,  having  each  degree  of  cold  work,  has  been  annealed  under 
the  following  conditions  : — 

All  the  test  pieces  requiring  the  same  anneal  were  pierced  with 
a  hole  at  one  end  and  threaded  on  to  the  same  piece  of  wire,  6-8  mm. 
apart,  so  as  to  be  immersed  simultaneously  in  the  annealing  bath, 
which  was  continuously  stirred. 

Shock  test  pieces  requiring  the  same  anneal  were  placed  in 
baskets  of  iron  wire  of  large  mesh,  and  immersed  in  the  bath  at  the 
same  time  as  the  corresponding  tensile  test  pieces. 

RESULTS. 

Dimensions  of  Tensile  Test  Pieces. 

Thickness  =  10  mm. 

Length  =  100  mm. 

Breadth  =15  mm. 

Approximate  area  =150  sq.  mm. 

The  area  of  cross  section  has  been  accurately  calculated  for  each 
test  piece. 

Gauge  length  =  ^66-678  =100  mm. 

Dimensions  of  Shock  Test  Pieces :  55  x  10  X 10  mm. 

A  round  groove,  2  mm.  in  depth,  leaving  a  residual  thickness 
of  8  mm. 

Impact  machine :  30  kg.  m.    Charpy  pendulum. 

167 


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APPENDIX  VI 

Paper  by  Lt.-Col.   Grard  on  the  Thermal  Treatment  of  Alloys  of 

Aluminium  of  Great  Strength 

Presented  to  L'Academie  des  Sciences,  by  Henri  Le  Chatelier,  Membre 
de  V Institute,  on  Sept.  22nd,  1919* 

THE  alloys  investigated  have  the  following  mean  composition  : — 

Copper 3-5  to  4% 

Magnesium  about     .          .         .          .  0-5  % 

Manganese      .....  0-5  to  1  % 

Aluminium-)- alumina -j- impurities      .  by  difference, 

and  correspond  with  the  type  of  light  alloy  of  great  strength  known 
as  "  Duralumin." 

The  object  of  this  paper  is  to  state  the  results  of  the  investigation 
on  the  variation  in  the  mechanical  properties  of  the  worked  alloy 
with  the  temperature  of  anneal  after  cold  work  and  with  the  rate 
of  cooling  subsequent  to  this  anneal. 

(a)  Method  of  Heating. 

By  immersion  in  oil  or  a  salt  bath  (sodium  nitrite,  potassium 
nitrate),  the  alloy  was  heated  to  a  series  of  temperatures,  rising 
by  fifty  degrees  from  the  normal  temperature  up  to  500°. 

(b)  Method  of  Cooling. 

Three  rates  of  cooling  were  employed,  namely  : — 

Rate  (i).  Very  slow  cooling  in  bath  (maximum  fall  in  tempera- 
ture, 100°  per  hour). 

Rate  (ii).       Cooling  in  air. 

Rate  (iii).  Cooling  by  immersion  in  water  at  20°,  i.e.  quenching 
in  water. 

During  the  first  eight  days  after  cooling,  tests  were  carried  out, 
and  showed  that  the  molecular  state  underwent  no  change  in  air 
during  this  period,  when  rate  of  cooling  (i),  as  above  defined,  had 
been  employed. 

On  the  other  hand,  the  use  of  rates  (ii)  or  (iii)  involves,  in  the  open 
air  during  these  eight  days,  certain  molecular  transformations, 
which  are  more  profound  in  the  case  of  rate  (iii)  (quenching in  water) 
than  in  that  of  rate  (ii)  (cooling  in  air). 

*  See  "  Comptes  rendus  hobdomadaires  des  Seances  de  1'Academie  de 
Sciences,"  Vol.  CLXIX,  No.  13,  Sept.  29th,  1919  (mecaniques,  physiques). 

174 


APPENDICES 


175 


These  changes,  inappreciable  for  annealing  temperatures  up  to 
300°,  become  more  pronounced,  for  both  rates  of  cooling,  with  rise 
of  annealing  temperature. 

After  eight  days,  the  mechanical  properties  remain  approximately 
the  same,  although  we  cannot  actually  foresee  the  ultimate  varia- 
tions in  the  future. 

In  every  case,  all  the  tests  given  below  were  carried  out,  what- 
ever the  temperature  of  anneal  and  rate  of  cooling,  eight  days  after 
the  completion  of  cooling. 

The  experiments  carried  out  show,  for  the  three  rates  of  cooling 
considered,  two  particularly  interesting  annealing  temperatures, 
namely,  350°  and  475°. 

Corresponding  with  each  of  these  temperatures  and  for  any  of 
the  three  rates  of  cooling,  there  is  a  maximum  Elongation  and 
Shock  Resistance  ;  but,  for  the  anneal  at  350°,  there  is  a  minimum 
of  the  other  mechanical  properties  (Tensile  Strength,  Elastic  Limit, 
and  Hardness),  whilst  there  is  a  maximum  of  these  latter  properties 
for  the  anneal  at  475°. 

In  the  following  table  which  summarises  the  results — 

Tensile  Strength  =the  greatest  stress  reached  during  the  test, 
expressed  in  kilograms  per  sq.  mm.  of 
initial  sections,  or  in  tons  per  sq.  in. 

Elastic  Limit        = Apparent  Elastic  Limit. 

Elongation  =%    Elongation    after    rupture,    using    the 

formula  of  the  type  : — 
L2  =66-67  where  L  =gauge  length. 
S  S  =  initial  section. 


Shock  Resistance 


= Shock  Resistance  or  "  Resilience  " — the  num- 
ber of  kilogram  metres  per  sq.  cm.,  neces- 
sary to  cause  the  rupture  by  impact  of  a  bar 
10x10x53-3  mm.  with  a  median  notch 
2  mm.  broad,  2  mm.  deep,  and  with  the 
bottom  rounded  off  to  1  mm.  radius. 


Temp, 
of 

A  nneal 
(degrees  C.) 

Bate 
of 
Cooling 

Tensile  Strength 
Kg              tons 

mm*                 In* 

Elastic  Limit 
Kg              tons 
mm2            in* 

Elonga- 
tion 
% 

Shock 
Resistance 
Kg.m 
cm* 

(i) 

20           12-7 

6            3-81 

20 

6 

350° 

(ii) 

20           127 

7             4-44 

20 

4-5 

(hi) 

20           12-7 

9            5-71 

15 

3 

(i) 

28           17-78 

12           7-62 

16 

4 

475° 

(ii) 

32           21-32 

18         11-42 

18 

4 

(iii) 

40           25-4 

20         12-7 

20 

4 

176  ALUMINIUM  AND  ITS  ALLOYS 

Two  treatments  stand  out,  namely  : — 

(1)  That  giving  the  metal  a  maximum  ductility,  or  a  softening 

treatment,  consisting  in  annealing  at  350°,  followed  by 
cooling,  rate  (i)  (100°  per  hour). 

(2)  That  giving  the  metal  maximum  tensile  properties,  or  the 

final  treatment,  consisting  in  annealing  at  475°,  followed 
by  cooling,  rate  (iii)  (quenching  in  water). 

Double  Quenching  from  475°. 

Double  quenching  from  475°,  carried  out  each  time  under  the 
conditions  previously  defined,  gives  duralumin  the  following 
properties  : — 

Tensile  Strength  =40  kg.  per  sq.  mm.  (25-4  tons  per  sq.  in.) 
Elastic  Limit        =23  kg.  per  sq.  mm.  (14-6  tons  per  sq.  in.) 
%  Elongation     =22 
Shock  Resistance=5  kg.  m.  per  sq.  cm. 

This  constitutes  the  optimum  final  heat  treatment. 

The  industrial  practice  of  a  softening  anneal  (annealing  at  350°, 
followed  by  cooling  rate  (i)  (100°  per  hour)),  which  has  just  been 
investigated  as  described  in  this  paper,  shows  that  this  intermediate 
treatment  is  of  real  use  for  drawing  and  pressing,  ensuring,  at  the 
same  time,  minimum  waste,  maximum  output,  and  maximum  life 
of  tools. 

We  give  a  set  of  curves*  of  the  mechanical  properties  correspond- 
ing with  different  anneals,  followed  by  cooling,  rate  (iii)  quenching 
in  water,  which  show  the  maxima  and  minima  for  this  particular 
heat  treatment. 

*  See  Fig.  53,  page  101. 


INDEX 


NAME  INDEX 


Anderson,  51-55,  56,  57 

Archbutt,  56 

Archbutt,  Rosenhain  and,  82 

Arnon, 117 

Bauer,  Heyn  and,  58 

Bayer,  4 

Bayliss,  and  Clark,  84 

Bernard,  and  Guillet,  84 

Breguet,  106 

Breuil,  117,  143 

Brislee,  57 

Campbell,  and  Mathews,  68,  117 

Carpenter,  and  Edwards,  68,  117 

Carpenter,  and  Taverner,  51 

Le  Chatelier,  68,  117 

Chevenard,  96,  121 

Clark,  Bayliss  and,  84 

Cowles-Kayser,  4 

Curry,  68,  117 

Ditte,  58 

Drouilly,  8 

Ducru,  59,  60 


Durville,  119 

Edwards,  Carpenter  and,  68,  117 

Escard,  82,  85 

Flusin,  6 

Guillet,  8,  9,  117 

Guillet,  and  Bernard,  84 

Gwyer,  56,  68,  117 

Hall,  6 

Heroult,  7 

Heyn,  and  Bauer,  58 

Kayser,  Cowles-,  4 

Lodin,  7 

Matthews,  Campbell  and,  68,  117 

Moldentrauer,  4 

Pecheux,  118 

Portevin,  117,  143 

Pryn,  5 

Robin,  142 

Rosenhain,  117 

Rosenhain,  and  Archbutt,  82 

St.  Claire  Deville,  4,  117 

Taverner,  Carpenter  and,  51 


SUBJECT  INDEX 


Abrasion,  resistance    of    cupro-alu- 

minium  to,  118 
Aeronautical  specifications,   French, 

151 

Ageing,  effect  of,  on  quenched  dur- 
alumin, 98,  104,  174 
Alloys — 

aluminium-copper — 
containing  4%  Cu,  76 
containing  8%  Cu,  76 
containing  12%  Cu,  78 
aluminium-copper-tin-nickel,  81 
aluminium-copper-zinc,  80 
aluminium -magnesium,  85 
aluminium-tin,  85 
aluminium -zinc,  82,  84 
casting,  71 

blowholes  in,  72 
density  of,  71 
extrusion  of,  84 


Alloys :  casting — 

hardness   of,   at  high   tempera- 

tures,  73 
lightness  of,  71 

mechanical  properties  of  (hard- 
ness, shock,  and  tensile),  76— 
85 

micrography  of,  86 
porosity  of,  72 
specific  heat  of,  74 
thermal  conductivity  of,  74 
classification  of,  xi,  67 
copper  as  constituent  of,  67 
copper-aluminium,equilibrium  dia- 
gram of,  68 
copper-aluminium.      See   "  Cupro- 

aluminium  " 
elektron,  85 
light — 

for  casting  purposes,  71 


178 


ALUMINIUM  AND  ITS  ALLOYS 


Alloys :  light — 

of   great   strength.    See    "  Dur- 
alumin " 
magnalium,  85 
magnesium-aluminium,  85 
soldering,  63 
zinc -aluminium,  84 
Alumina — 

electrolysis  of,  4 

estimation  of,  in  aluminium,  149 
importance  of,  as  impurity,  17,  63 
melting     point     of     mixtures     of 

cryolite  and,  5 
production  of — 

from  bauxite,  3 

from  clay,  4 
works  producing,  13 
Aluminium — 

analysis  of,  16,  147 
annealing  of,  30,  160,  169 
annealed — 

Anderson's  work  on,  51,  54 

cupping  properties  of,  44,  52 

discussion  on,  49 

hardness  of,  39,  51 

shock  resistance  of,  41 

structure  of,  57 

tensile  properties  of,  29,  34 
atomic  weight  of,  15 
casting  of,  8 

coefficient  of  expansion  of,  62 
cold  working  of,  20 
c  old  -worked — 

Anderson's  work  on,  51 

corrosion  of,  58 

cupping  properties  of,  41 

discussion  on,  48 

hardness  of,  36-38 

shock  resistance  of,  38 

structure  of,  57 

tensile  properties  of,  20 
commercial,  impurities  in,  16 
companies  producing,  12 
conductivity  of,  15 
corrosion  of,  58 
cost  price  of,  7 
cupping  tests — 

on  annealed,  44,  52 

on  cold-worked,  41 
density  of,  15 
dust,  8 
effect  of  atmospheric  agencies  on, 

58 

Erichsen  tests  on,  52 
estimation  of,  147,  148 
extraction  of,  4 
extrusion  of,  8 
fluoride,  6 
foil,  8 
grading  of,  16 


Aluminium — 
hardness — 

of  annealed,  39,  51 
of  cold-worked,  36-38 
impact    tests    on.       See    "  Shock 

Resistance  of  " 
impurities  in  commercial,  16 
mechanical    properties     of.       See 
"Hardness,"  "Shock  Resist- 
ance," "  Cupping  Properties," 
"  Tensile  Properties  " 
melting  point  of,  15 
micrography  of,  56 
nitride,  production  of,  4 
output  of,  6,  12 

oxidation     of,     during     manufac- 
ture, 5 

physical  properties  of,  15 
polishing  of,  56 
recrystallisation  of,  53 
rolling  of,  7 
shock  resistance — 
of  annealed,  41 
of  cold-worked,  38 
soldering  of,  52 
specifications  for,  151 
specific  heat  of,  15 
specific  resistance  of,  15 
sulphate,  4 
tensile  properties — 
of  annealed,  29,  34 
of  cold-worked,  20 
test  pieces — 

dimensions  of,  19 
standard,  152 

thermal  conductivity  of,   15 
welding  of,  63 

works  producing,  situation  of,  12 
world's  production  of,  12 
Aluminium  bronze,  67.    See  "  Cupro- 

aluminium  " 

Ammonia,  production  of,  4 
Analysis  of — 

aluminium-copper  alloys,  76,  78 
aluminium-copper-tin-nickel  alloy, 

81 

aluminium-copper-zinc  alloy,  80 
cold-worked  aluminium  sheet,  22, 

25 

cupro  aluminium,  121,  132,  137 
duralumin,  87 

light  alloys  of  great  strength,  87 
Analysis,  methods  of,  147 
Annealing — 

aluminium  sheet — 

duration  of,  30,  160,  169 
effect  on  cupping  properties  of, 

44 

effect  on  hardness  of,  39,  52 
effect  on  shock  resistance  of,  41 


INDEX 


179 


Annealing :  aluminium  sheet — 
effect  on  structure  of,  57 
effect  on  tensile  properties  of,  29, 

34 

general  discussion  on,  49 
intermediate  and  over- annealing, 

54,  55 

methods  of,  30,  160,  169 
scleroscope  values  as  measure  of, 

51 

stages  in,  31 

Anderson's  work  on,  51 
cupro-aluminium — 

Type    I,    effect    on    mechanical 

properties  of  cast,  122 
Type    I,    effect    on    mechanical 

properties  of  forged,  123 
Type  I,  effect  on  microstructure 

of,  143 
Type  II,  effect  on  mechanical 

properties  of,  132 
Type  II,  effect  on  microstructure 

of,  145 
Type  III,  effect  on  mechanical 

properties  of,  139 
Type  III,  effect  on  microstruc- 
ture of,  145 
duralumin — 

effect  on  mechanical  properties 

of  cold-worked,  89 
methods  of,  89,  91 
Anthracite,  16 
Atmospheric  agencies,  effect  of,  on 

aluminium,  58 
Autogenous  welding  of  aluminium,  63 

Bars,  specifications  for,  153 
Bauxite — 

composition  of,  3 

occurrence  of,  3 

treatment  of,  4 

world's  production  of,  9 
Bending  tests,  specifications  for,  154 
Billets,  dimensions  of,  8 
Blowholes  in  castings,  72 
Brass — 

author's  work  on,  20 

corrosion  of,  59 

Breaking  load.    See  "  Cupping  tests  " 
Brinell  hardness.    See  "  Hardness  " 
Bronze,  aluminium,  67.    See11  Cupro- 
aluminium  " 

Cadmium,  in  aluminium -zinc  alloys, 

84 
Calcium   fluoride,   melting   point   of 

mixtures  containing,  6 
Calcium  fluoride,  use  in  manufacture 

of  synthetic  cryolite,  4 
Carbon,  gas,  16 


Castings — 

aluminium,  structure  of,  57 
aluminium  alloy — 

chill,  method  of  casting,  75 
chill,  properties  of,  76,  78,  80,  81 
sand,  method  of  casting,  75 
sand,  properties  of,  76,  78,  80,  81. 
See   individual    alloys    under 

"  Alloys  " 
aluminium  alloys,  light,  for.    See 

"Alloys,"   71 
cupro-aluminium — 

difficulties  in  casting,  119 
micrography  of,   145 
suitability  for,  119 
effect  of  tin  on,  85 
requisite  properties  of  alloys  for,  71 
test  pieces,  methods  of  preparing, 

75 

Chalais  Meudon  Laboratory,  20,  41 
Chromic  acid,  use  of,  in  micrography, 

56 

Coke,  petroleum,  16 
Cold  work — 

aluminium  sheet — 

effect  on  corrosion  of,  58 
effect  on  cupping  properties  of, 41 
effect  on  hardness  of,  36-38 
effect  on  micrography  of,  57 
effect  on  shock  resistance  of,  38 
effect  on  tensile  properties  of,  20 
general  discussion  on,  48 
Anderson's  work  on,  51 
definition  of — 
Anderson's,  51 
author's,  20 
duralumin,    effect    on    mechanical 

properties  of,  89 
method     of     obtaining     specified 

degree  of,  20 
Conservatoire  des  Arts  et  Metiers,  20, 

38 
Constituents,  micrographic — 

in  aluminium -copper  alloys,  70,  86 
in  cupro-ahuninium,  69,  142 
martensitic    in    cupro-aluminium, 

143 
Cooling — 

hardening  after,  87 

rates  of,  standard,  92,  174 

duralumin,  effect  on  properties  of, 

92,  111,  174 

quenching,  (rate  iii),  97,  174 
Copper — 

as  constituent  of  alloys,  67,  68 
aluminium  -  copper    alloys.        See 

"Alloys" 
copper-aluminium      alloys.        See 

"  Cupro-aluminium  " 
estimation  of,  148 


180 


ALUMINIUM  AND  ITS  ALLOYS 


Corundum,  artificial,  4 
Critical  points — 

of  cupro- aluminium,  121,  132,  137 
of  duralumin,  96 

Crushing  tests,  specification  for,  154 
Cryolite — 

melting     point     of     mixtures     of 

alumina  and,  5 
occurrence  of,  4 
synthetic,  4 
Cupping  tests — 

Erichsen  apparatus  for,  52 
Persoz  apparatus  for,  41 
results  of — 

on  aluminium,  annealed,  44 
on  aluminium,  cold  worked,  41 
on  duralumin  after  heat  treat- 
ment, 114 

specifications  for,  154 
Cupro-aluminium — 
casting — 

difficulties  in,  119 
suitability  for,  119 
composition  limits,  117 
dimensions  of  test  pieces  of,  120 
forging,  suitability  for,  119 
micrography  of,  68,  142 
properties,  chemical  and  physical, 

118 
resistance  to  wear  and  abrasion, 

118 

specific  resistance  of,  118 
stamping,  suitability  for,  119 
types  of,  117 
Type  I — 

analysis  of,  121 
critical  points  of,  121 
density  of,  121 

hardness  of,  at  high  tempera- 
tures, 130 

mechanical  properties  of  cast, 
with  annealing  temperature, 
122 

mechanical  properties  of  cast, 
with  quenching  temperature, 
124 

mechanical  properties  of  forged, 
with  annealing  temperature, 
123 

mechanical  properties  of  forged, 
with  quenching  temperature, 
127 

mechanical  properties  of  forged, 
with  reannealing  temperature 
after  quenching,  127 
micrography  of  cast,  145 
micrography  of  forged,  143 
micrography  of   forged  and  re- 

annealed,  143 
micrography  of  quenched,  144 


Cupro-aluminium :  Type  I — 

micrography  of  quenched  and 
reannealed,  145 

optimum  thermal  treatment  for, 

136 
Type  II— 

analysis  of,  132 

critical  points  of,  132 

density  of,  132 

hardness  of,  at  high  tempera- 
tures, 137 

mechanical  properties  of  forged, 
with  annealing  temperature, 
132 

mechanical  properties  of  forged, 
with  quenching  temperature, 
133 

mechanical  properties  of  forged, 
with  reannealing  temperature 
after  quenching,  134 

micrography  of,  145 

optimum  thermal  treatment  for, 

136 

Type  Ill- 
analysis  of,  137 

critical  points  of,  137 

density  of,  137 

hardness  of,  at  high  tempera- 
tures, 141 

mechanical  properties  of  forged. 
with  annealing  temperature, 
139 

mechanical  properties  of  forged, 
with  quenching  temperature, 
140 

mechanical  properties  of  forged 
with  reannealing  tempera- 
ture after  quenching,  141 

micrography  of,  145 

optimum  method  of  working, 
141 

uses  of,  119 

Dendritic      structure    of    cast    alu- 
minium, 57 

Dendritic   structure    of    constituent 
in  cupro-aluminium,  Type  I, 
143 
Density — 

of  alloys  for  casting,  71 
of  aluminium,  6,  15 
of  aluminium-copper  alloy — 
containing  4%  Cu,  76 
containing  8%  Cu,  76 
containing  12%  Cu,  78 
of    aluminium  -  copper  -  tin  -  nickel 

alloy,  82 

of  aluminium-copper-zinc  alloy,  80 
of  cryolite -alumina  bath  for  elec- 
trolysis, 6 


INDEX 


181 


Density — 

of  cupro-aluminium,  118 
Type  I,  121 
Type  II,  132 
Type  III,  137 
of    magnesium -aluminium    alloys, 

85 

of  molten  aluminium,  6 
Dilatometer,  96,  121,  132,  137 
Drawing,  requirements  of  sheet  for, 

52 
Drifting     tests,     specifications    for, 

154 
Duralumin — 

ageing  after  quenching,   98,    104, 

174 

analysis  of,  87,  174 
critical  points  of,  96 
dimensions  of  test  pieces  of,  89 
cupping  tests,  after  thermal  treat- 
ment, 114 

hardness  tests,  at  high  tempera- 
tures, 116 
maxima    and    minima    in    tensile 

properties  of,  94,  176 
mechanical  properties  of — 

after  annealing,   worked    alloy, 

89 

after  cold  work,  90 
after  quenching,  worked  alloy, 

98,  174 

after  quenching,  cast  alloy,  102 
after  double  quenching,  113,  176 
after  reannealing,  quenched  al- 
loy, 110 
effect  of  rate  of  cooling,  after 

reannealing,  111 
methods  of  annealing  of,  89,  91, 

174 

paper  by  Lt.-Col.  Grard  on,  174 
practical  treatment  of,  113 
quenching — 

attainment  of  equilibrium  after, 

108 
mechanical  properties  after,  98, 

102 
specifications  for,  153 

Elastic  limit,  determination  of,  151. 

See  "  Tensile  Properties  " 
Electric  furnaces — 

description  of,  4 

regulation  of,  4 

tapping  of,  5 
Electrodes — 

composition  of,  16 

usage  of,  6 
Elektron,  85 

Elongation,   determination    of,    151. 
See  "Tensile  Properties  " 


Equilibrium — 

attainment  of,  by  duralumin  after 

quenching,  108 

diagram  of  copper-aluminium  sys- 
tem, 68 

Erichsen  apparatus,  52 
Erichsen  tests  on  aluminium  (Ander- 
son), 52 

Etching  of  aluminium,  56 
Etching  of  cupro-aluminium,  142 
Eutectic — 

a +7,  of  copper-aluminium  alloys, 

69,  142,  143 
i7+CuA!2,  70,  86 
appearance  of,  (0+7),  143 
solution  *'  M,"  144 
Expansion,    coefficient    of,    of    alu- 
minium, 62 

Extrusion  of  aluminium,  8 
Extrusionof  zinc -aluminium  alloys,  84 

Fluor-spar,  4 

Flux  for  soldering,  63 

Forged  alloys — 

properties    of   forged    aluminium - 

copper  alloy  (4%  Cu),  76 
structure  of  forged  cupro-alumin- 
ium, Type  I,  143 
suitability  of  cupro-aluminium  for 

forging,  119 
Furnaces,  electric,  4,  5 
Furnaces  for  remelting  aluminium,  7 

Gauge  length,  standard,  152 
Grading  of  aluminium,  17 
Grain  size — 

gross,     apparent,     in     cupro-alu- 
minium, 143 

in  aluminium  sheet,  52 

Hardening   of    alloys   due   to  mag- 
nesium, 87 
Hardness — 
Brinell — 

of  aluminium,  thick  sheet,  an- 
nealed, 38 

of  aluminium,  thick  sheet,  cold 
worked,  36 

of  aluminium -copper  alloy,  con- 
taining 4%  Cu,  at  high  tem- 
peratures, 76 

of  aluminium -copper  alloy,  con- 
taining 8%  Cu,  at  high 
temperatures,  78 

of  aluminium -copper  alloy,  con- 
taining 12%  Cu,  at  high 
temperatures,  78 

of  aluminium-copper-tin-nickel 
alloy,  at  high  temperatures, 
82  * 


182 


ALUMINIUM  AND  ITS  ALLOYS 


Hardness :  Brinell — 

of  aluruinium-copper-zinc  alloy, 
at  high  temperatures,  80 

of  aluminium-zinc  alloys,  at  high 
temperatures,  84 

of  casting  alloys,  at  high  tem- 
peratures, 73 

of  cupro-aluminium,  Type  I,  at 
high  temperatures,  130 

of  cupro-aluminium,  Type  II,  at 
high  temperatures,  137 

of  cupro-aluminium,  Type  III,  at 
high  temperatures,  141 

of  duralumin,  at  high  tempera- 
tures, 116 

of  duralumin,  after  quenching, 

102,  104 
scleroscope — 

of   aluminium,   thin   sheet,   an- 
nealed, 38 

of   aluminium,   thin   sheet,   an- 
nealed (Anderson),  53 

of  aluminium,  thin  sheet,  cold 
worked,  38 

as  a  measure  of  complete  anneal 

(Anderson),  51 
Heat     treatment.       See     "Thermal 

Treatment " 

Hydrofluoric  acid — use  as  etching 
reagent,  57 

Impact  tests.  See  "  Shock  Resist- 
ance " 

Impurities — 

in  aluminium,  16 

effect  of,  on  soldering,  62 

estimation  of,  in  aluminium,  148 

Iron — 

as  impurity  as  in  aluminium,  16,  62 
estimation  of,  148 
oxide  of,  in  bauxite,  3 

Laboratories,  testing,  ix 

Laboratory,  Chalais  Meudon,  20,  41 

Laboratory,  Conservatoire  des  Arts 
et  Metiers,  20,  155,  159 

Literature,  contemporary,  on  alu- 
minium, 51 

Magnalium,  85 
Magnesium — 

aluminium -magnesium  alloys,  85 

cause  of  hardening  after  quench- 
ing, 87 

estimation  of,  148 

magnesium-aluminium  alloys,85,86 
Melting  point — 

of  aluminium,  15,  62 

of   mixture    of  cryolite,   alumina, 
and  fluorides,  5 


Micrography — 
of  aluminium,  56 
of  casting  alloys,  86 
of  cupro-aluminium,  142 

Nickel,aluminium  alloys  containing,  8 1 

estimation  of,  148 
Nitric  acid,  use  in  micrography,  57 

Paraffin,  use  in  micrography,  56 
Polishing  of  aluminium.  56 
Porosity  of  castings,  56 
Potash,  use  of,  as  etching  reagent, 

56 

Potassium  nitrate,  30,  89,  92 
Preservation  of  aluminium,  58 
Pressing,  requirements  of  sheet  for, 

41 
Pressing,  effect  of,  on  corrosion  of 

aluminium,  58 
Properties — 

chemical,  of  cupro-aluminium,  118 
mechanical.         See    "  Cupping," 
"Hardness,"        "Tensile," 
"  Shock  " 
physical — 

of  aluminium,  15 

of     aluminium,     effect     of,     on 

soldering,  62 
of  casting  alloys,  71 
of  cupro-aluminium,  118 

Quenching — 

ageing  after,  98,  104 

attainment  of  equilibrium  after,  108 

of  cast  duralumin,  102 

double,  113,  176 

effect  of — 

on     mechanical     properties     of 

duralumin,  97,  174 
on     mechanical     properties    of 
cupro-aluminium,      Type      I, 
cast,  124 

on  mechanical  properties  of 
cupro-aluminium,  Type  I, 
forged,  125 

on     mechanical     properties     of 

cupro-aluminium,  Type  II,  133 

on    mechanical     properties     of 

cupro-aluminium,    Type    III, 

140 

on    micrography    of    cupro-alu- 
minium, Type  I,  144 
reannealing  after,  110 
treatment  preparatory  to,  97 

Reannealing — 
effect  of — 

on  quenched  duralumin,  110 
on   quenched  cupro-aluminium, 
Type  I,  127 


INDEX 


183 


Reannealing :  effect  of — 

ori  quenched   cupro-aluminium, 

Type  II,  134 
on  quenched   cupro-aluminium, 

Type  III,  141 

on    micrography    of    cupro-alu- 
minium, 145 
varying  rates    of  cooling  after, 

111 

methods  of,  110 
Recrystallisation  of  aluminium :  effect 

of  prior  cold  work,  53 
Reduction  of  area  (Anderson),  51 
Resilience,     definition      of     (see     p. 
vii),    175.      See  also    "Shock 
Resistance  " 
Robin's  reagent,  142 
Rolling  of  aluminium,  7 


Scleroscope.    See  "  Hardness  " 
Sections,  production  of,  8 
Sections,  specifications  for,  153 
Sheet — 

rolling  of  aluminium,  7,  8 

specifications  for,  151 
Shock  resistance — 

definition  of,  vii,  175 

determination  of,  38 

of  aluminium,  annealed,  41 

of  aluminium,  cold  worked,  38 

of  casting  alloys — 
4%  Cu,  76 
8%  Cu,  78 
12%  Cu,  78 
Al-Cu-Sn-Ni,  81 
Al-Cu-Zn,  80 

of  cupro-aluminium — 

Type  I,  cast,  annealed,  122 
Type  I,  cast,  quenched,  124 
Type  I,  forged,  annealed,  123 
Type  I,  forged,  quenched,  125 
Type  I,  forged,  reannealed,  127 
Type  II,  forged,  annealed,  132 
Type  II,  forged,  quenched,  133 
Type  II,  forged,  reannealed,  134 
Type  III,  forged,  annealed,  139 
Type  III,  forged,  quenched,  140 
Type    III,    forged,    reannealed, 
141 

of  duralumin — 
cold  worked,  89 
double  quenched,  113 
quenched,  98,  104 
reannealed,  111 
Silica  in  bauxite,  3 
Silicon — 

estimation  of,  in  aluminium,  147, 
149 

as  impurity  in  aluminium,  16,  62 


Slabs,  dimensions  of,  7 
Soda,  use  as  etching  reagent,  56 
Sodium  nitrite,  30,  89,  92 
Soldering — 

alloys    for    use   in    soldering    alu- 
minium, 63 
of  aluminium,  62 
Specific  heat — 
of  aluminium,  15 
of  casting  alloys,  74 
Specific  resistance — 
of  aluminium,  15 
of  cupro-aluminium,  118 
Specifications,    French  aeronautical, 
for  aluminium  and  alloys  of 
great  strength,  151 
Stamping,  suitability    of   cupro-alu- 
minium for,  151 
Strip,  aluminium,  specifications  for, 

151 
Structure.    See  "  Micrography  " 


Tar,   as   binding   material   for   elec- 
trodes, 16 

Telegraph    wires,    corrosion    of    alu- 
minium, 59 
Tensile  properties — 

of  aluminium — 
annealed,  34 
cold  worked,  21 

of  aluminium-copper  alloy — 
4%  Cu,  76 
8%  Cu,  78 
12%  Cu,  78 

of    aluminium  -  copper  -  tin  -  nickel 
alloy,  81 

of     aluminium-copper-zinc     alloy, 
80 

of  aluminium -zinc  alloys,  82 

of  casting  alloys,  72 

of  cupro-aluminium — 

Type  I,  cast,  annealed,  122 
Type  I,  cast,  quenched,  124 
Type  I,  forged,  annealed,  123 
Type  I,  forged,  quenched,  125 
Type  I,  forged,  reannealed,  127 
Type  II,  forged,  annealed,  132 
Type  II,  forged,  quenched,  133 
Type  II,  forged,  reannealed,  134 
Type  III,  forged,  annealed,  139 
Type  III,  forged,  quenched,  140 
Type  III,  forged,  reannealed,  141 

of  duralumin — 
cold  worked,  89 
double  quenched,  113,  175 
maxima  and  minima,  after  heat 

treatment,  94 
quenched,  98,  104,  175 
reannealed,  111 


184 


ALUMINIUM  AND  ITS  ALLOYS 


Tensile  properties— 

standard  methods  for  determining, 

151 

Tensile  test  pieces — 
dimensions  of — 
aluminium,  19 
aluminium,  standard,  152 
casting  alloys,  75 
cupro -aluminium,  120 
duralumin,  89 
methods  for  casting,  75 
Thermal  conductivity — 
of  aluminium,  15 
of  casting  alloys,  74 
Thermal  treatment — 
effect  of — 

on  cupping  properties  of  duralu- 
min, 114 

on  tensile  properties  of  duralu- 
min, 92,  104 
optimum — 

for  cupro-aluminium,  Type  1, 130 
for    cupro-aluminium,  Type   II, 

136 
for  cupro-aluminium,  Type  III, 

141 
practical,  for  duralumin,  113,  175 


Tin— 

aluminium-copper-tin-nickel  alloy, 

81 

aluminium-tin  alloys,  85 
addition  of,  in  casting,  85 
estimation  of,  in  aluminium,  148 
Titanium,  as  impurity  in  aluminium, 

17 

Tripoli,  use  in  micrography,  56 
Tubes,  methods  of  carrying  out  tests 

on,  153 
Tubes,  specifications  for,  153 

Units.     See  p.  vii 

Utensils,  corrosion  of  culinary,  3,  7 

Water  power,  60 
Welding  of  aluminium,  63 

Zeppelin  L  49,  85 
Zinc — 

aluminium-copper-zinc  alloy,  80 
aluminium -zinc  alloys — 
Brinell  hardness  of,  84 
effect  of  temperature  on,  82 
estimation  of,  in  aluminium,  148 
zinc -aluminium  alloys,  84 


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